Cholesteric liquid crystal writing device with stylus eraser

Abstract

The present application relates to a cholesteric liquid crystal writing device with a stylus eraser. A liquid crystal writing device is erasable by a stylus. The liquid crystal writing device includes a liquid crystal layer comprising a cholesteric liquid crystal material. A user applies pressure to a flexible substrate, which changes the reflectivity of the cholesteric liquid crystal material to form an image on the liquid crystal writing device. The liquid crystal layer is disposed between conductive layers. The writing device terminals are conductive and connected to the conductive layers. The stylus includes stylus electronics adapted to apply an erase voltage or erase voltage waveform to the writing device terminals.

Description

Technical Field

[0001] The present disclosure relates generally to liquid crystal writing devices, and in particular to cholesteric liquid crystal pressure sensitive writing devices. background

[0002] In 2010, Kent Displays Inc.'s Boogie Pressure-sensitive cholesteric liquid crystal writing devices, also known as electronic writers (eWriter), are on the market. A slight pressure of a pointed stylus or fingernail can be used to write or trace an image on the surface of the writing device, as described in U.S. Patents Nos. 6,104,448 and 9,116,379, both of which are incorporated herein by reference. In a cholesteric liquid crystal writing device, the liquid crystal is sandwiched between two substrates separated by a specific cell gap. The upper substrate is flexible and the bottom substrate is opaque, translucent, or possibly transparent, with an opaque or translucent coating or layer below serving as a background. Within the cell gap is a bistable cholesteric liquid crystal layer that can exhibit two textures, a substantially transparent (focal conic) texture and a colored reflective (planar) texture. The spacing of the cell gap is typically affected by the use of plastic or glass spacers that are cylindrical or spherical in shape. Spacers are also used to control pressure sensitivity, as described in U.S. Patent No. 8,947,604. In its normal operating mode, one presses the top substrate with a pointed stylus or fingernail to change the liquid crystal optical texture from a focal conic transparent texture to a bright reflective colored planar texture at the location of the stylus. The reflected color contrasts well with the opaque or translucent color of the liquid crystal layer below. The image traced by the stylus or fingernail will remain on the electronic writer indefinitely without the application of voltage until erased. The electronic writer is cleared by applying a voltage pulse to the upper transparent conductive layer and the lower optional transparent conductive layer on the inner surface of the substrate to achieve erasure, which drives the cholesteric liquid crystal from its colored reflective state back to its focal conic substantially transparent state. Various pulse sequences have been discovered to erase the image. Typically, these pulse sequences include pulses of sufficient voltage to first drive the material to an untwist, homeotropic state and thereby remove the characteristic twisted cholesteric structure of the liquid crystal. This further completely clears the image before driving the material to the focal conic texture. The above principles are disclosed in more detail in US Pat. Nos. 6,104,448 and 10,558,065, both of which are incorporated herein by reference.

[0003] As disclosed in U.S. Patent No. 5,493,430 (which is incorporated herein by reference), the color of the background is additively mixed with the color reflected by the cholesteric liquid crystal to present a color different from the color of the cholesteric liquid crystal. The background can have multiple colors, and these colors can be patterned, as described in U.S. Patent No. 9,235,075, which is incorporated herein by reference. The reflected color from the liquid crystal layer can also be patterned, as described in U.S. Patent No. 9,927,672.

[0004] Existing technology Figure 1 Components of a cholesteric liquid crystal writing element 10 are shown. Figure 1 A light-absorbing coating 1 is disposed on a lower transparent polymer substrate 2, and an optional transparent conductive layer 3 is coated on the other surface of the lower transparent polymer substrate 2. The coating 1 can also be patterned, as described in U.S. Patent 9,235,075. The remainder of the pressure-sensitive liquid crystal device includes a liquid crystal layer 4 and spacers, and a transparent upper substrate 6, the liquid crystal layer 4 comprising a cured dispersion of cholesteric liquid crystal and polymer, which is coated on its inner surface with a transparent conductive layer 5. The side of the upper substrate 6 not coated with the conductor 5 forms a writing surface W that is close to an observer or user V of the device (observer V is looking in the general direction of the arrow). The lower and upper substrates with conductors extend to form a bottom protrusion 7 and a top protrusion 8. The transparent conductive layers 3 and 5 are exposed on the protrusions 7 and 8, respectively, for connection to drive electronics so that a voltage or multiple voltage pulses of a size and pulse width suitable for clearing or erasing an image can be applied to the conductive layers 3 and 5.

[0005] Figure 2 Commercially available Boogie Illustration of a writing device showing a liquid crystal layer 4 having an unreduced cell gap 29 and a region of reduced cell gap 30 due to pressure from a stylus 14, which is a pointed, untethered object. Conductive electrodes 3 and 5 on projections 7 and 8, respectively, are connected via electrical interconnects 27 to an electronic erasing circuit 31, which provides appropriate voltages (typically in the form of voltage pulses) to the conductive electrodes 3 and 5 to erase and clear the writing device for a new image. Pressure from the stylus 14 is applied to create an image.

[0006] U.S. Patent 9,651,813 discloses another version of a writing device in which the erasing circuit is removed from the cholesteric liquid crystal writing device. Dubbed Liquid Crystal Paper, the patent discloses two separate electronic devices into which the liquid crystal paper must be inserted and properly positioned for electrical connection in order to erase the image. One advantage of the liquid crystal paper is that it can have similar properties to regular writing paper, but unlike regular paper, the liquid crystal paper is not discarded after use; the liquid crystal paper can be cleared and reused multiple times. People use the liquid crystal paper to write or draw in the same way as regular paper. An untethered pointed stylus is used to write on the liquid crystal paper, but the advantage of the pointed stylus is that it does not have to be a pencil or pen, but rather a pointed object, such as a person's fingernail. The liquid crystal paper, like regular paper, is placed on a hard surface for writing. One inconvenience of the prior art liquid crystal paper is that it needs to be picked up and moved to the erasing device and electrically contacted in order to erase it.

[0007] Existing technology cannot mimic a pencil on paper because handheld styluses lack the ability to write and erase or erase the writing device. When using a pencil on paper, people are accustomed to writing with one end of the pencil and erasing with the other. Therefore, if a stylus for a writing device could do the same, then the stylus could have a handheld eraser on the end opposite the tip for erasing or clearing the writing device, which would be a convenient addition to the technology. It would be a further advantage if the eraser could perform like a pencil, allowing images to be quickly and easily erased.

[0008] Overview of the Disclosure

[0009] A cholesteric liquid crystal writing device and stylus suitable for erasing are disclosed, wherein the erasing electronics are part of the stylus itself. Similar to a conventional pencil, the stylus has an erasing component (eraser) on its end opposite the tip. One can erase the writing device by simply turning the stylus over and making electrical contact with the erasing component. In one example, intelligent electronics allow the stylus to detect when the stylus is in electrical contact with the writing device and apply an appropriate voltage pulse to erase the device. The disclosed device brings the functionality of the cholesteric liquid crystal writing device closer to that of a conventional pencil on paper, because the stylus not only writes on paper, but is also used to erase paper.

[0010] A first aspect of the present disclosure features a stylus and a liquid crystal writing device erased by the stylus. The liquid crystal writing device includes a cholesteric liquid crystal material. A user applies pressure to a flexible surface, which changes the reflectivity of the cholesteric liquid crystal material to form an image on the liquid crystal writing device. The liquid crystal layer is disposed between conductive layers. The writing device terminals are conductive and connected to the conductive layers. The stylus includes stylus electronics adapted to apply an erase voltage to the writing device terminals.

[0011] With reference to the more specific features of the first aspect, unless otherwise indicated, in the first feature, the stylus electronics are adapted to detect electrical contact with the writing device terminals and automatically apply an erase voltage to the writing device terminals. This unique feature allows the stylus itself to apply the erase voltage without requiring the user to activate a switch. Another second feature further limits the first feature, wherein the stylus includes a power source and the stylus electronics, and wherein an optional resistor is connected between the writing device terminals. A third feature further limits the second feature, wherein the stylus includes a writing tip.

[0012] Furthermore, a switch is provided on the stylus, wherein the stylus electronics are adapted to apply an erase voltage to the writing device terminal when activated by the switch. In another feature, the stylus includes a button that activates the switch when pressed. In yet another feature, the stylus includes a spring-loaded stylus terminal that engages one of the writing device terminals, wherein the spring-loaded stylus terminal activates the switch when the spring is compressed.

[0013] Another feature is that the cholesteric liquid crystal material includes a dispersion of cholesteric liquid crystal and a polymer, and includes spacers.

[0014] Another feature is that the erase voltage is an erase portion of a slow-discharge waveform, and the stylus electronics are adapted to apply the erase portion of the slow-discharge waveform to the writing device terminals. In another feature, the liquid crystal writing device is adapted to apply the discharge portion of the slow-discharge waveform such that the slow-discharge waveform erases at least one image.

[0015] Another feature is that the erase voltage is an erase portion of a slow discharge waveform. The stylus electronics are adapted to apply the erase portion of the slow discharge waveform to the writing device terminals. A resistor having a resistance value is connected between the liquid crystal writing device terminals. In yet another feature, the product of the resistance value and the effective capacitance of the liquid crystal layer results in a discharge time value that results in erasure of at least one image.

[0016] Another feature is that the erase voltage is an erase portion of a slow discharge waveform. The stylus electronics are adapted to apply the erase portion of the slow discharge waveform to the writing device terminals. The effective resistance of the liquid crystal layer causes the discharge and erasure of the at least one image. In another feature, the product of the effective resistance and the effective capacitance of the liquid crystal layer results in a discharge time value that causes the erasure of the at least one image.

[0017] In another feature, the erase voltage includes an erase voltage waveform.

[0018] In another feature, the user applies pressure to the stylus, which, without applying a voltage, changes the reflectivity of the reflective liquid crystal material from a colored reflective texture to a transparent texture to form an image on the writing device.

[0019] In yet another feature, the user applies pressure to the stylus, which changes the reflectivity of the reflective liquid crystal material from a transparent texture to a colored reflective texture to form an image on the writing device.

[0020] In a second aspect of the present disclosure further limiting the first aspect, the stylus comprises:

[0021] a stylus terminal that is electrically conductive and adapted to engage a writing device terminal, and

[0022] The stylus terminal includes a first stylus terminal and a second stylus terminal separated from the first stylus terminal.

[0023] Referring now to a specific feature of the second aspect, the first stylus terminal has a circular shape or a shape having a portion of a circle. In another feature, the second stylus terminal has a ring shape or a shape having a portion of a ring. In yet another feature, the first stylus terminal includes a circular protrusion, and the second stylus terminal includes a ring. The circular protrusion is located within the ring.

[0024] In a third aspect of the present disclosure, which further limits the first aspect, a stylus pen and a liquid crystal writing device include:

[0025] case;

[0026] wherein the liquid crystal layer and the conductive layer are contained in a housing, and the housing forms a frame around the flexible surface; and

[0027] The writing device terminal is arranged on the outer surface of the housing.

[0028] In light of this disclosure, one of ordinary skill in the art will appreciate that, in all aspects, a stylus can have a nib for improving writing performance, or it can lack a nib for improving writing performance. This is because writing on a liquid crystal writing device can be accomplished by simple pressure from any object, even a fingernail, or for that matter, any part of the stylus that can apply localized pressure to the liquid crystal device. If a nib is present, the nib can control the width of the written line. The nib can be solid, so that no material is left on the writing surface, or it can dispense a material such as ink, lead, or marker onto the writing surface.

[0029] A fourth aspect of the present disclosure generally relates to a stylus pen for erasing a liquid crystal writing device, the stylus pen comprising:

[0030] A battery disposed inside the stylus;

[0031] an erasing electronic device, which is disposed inside the stylus and powered by a battery, and is adapted to generate an erasing voltage;

[0032] Conductive stylus terminals; and

[0033] The erasing electronic device is adapted to detect electrical contact with a writing device terminal of the liquid crystal writing device and automatically apply an erasing voltage to the writing device terminal.

[0034] With reference to more specific features of the fourth aspect, the erase voltage is an erase portion of a slow discharge waveform, and the erase electronics are adapted to apply the erase portion of the slow discharge waveform to the writing device terminals.

[0035] Many additional features, advantages and a more comprehensive understanding of the present disclosure will be obtained from the accompanying drawings and the following detailed description. It should be understood that the above summary of the present disclosure describes the subject matter of the present disclosure in broad terms, while the following detailed description describes the subject matter of the present disclosure in more detail and presents specific embodiments, which should not be interpreted as necessarily limiting the broad subject matter of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 : Illustration of components of a prior art cholesteric liquid crystal writing element;

[0037] Figure 2 : Prior Art Boogie an illustration of a side view of a liquid crystal writing device;

[0038] Figure 3 : Illustration of the disclosed concept of a stylus for erasing a writing device;

[0039] Figure 4A and Figure 4B : Illustration of different types of example terminals on a stylus and writing device;

[0040] Figure 5 : A diagram of the internal circuitry of a writing device;

[0041] Figure 6 : Illustration of a prior art electronic waveform for an erase writing device;

[0042] Figure 7 : Illustration of the electronic waveform of the slow discharge erasure of the writing device in Example 1;

[0043] Figure 8 : Schematic diagram of a stylus detection and drive circuit for an erasable writing device;

[0044] Figure 9 : Schematic diagram of the circuit of Example 1;

[0045] Figure 10 : Schematic illustration of a circuit for manually erasing an image;

[0046] Figure 11 : An illustration of a stylus being erased using a button-activated switch; and

[0047] Figure 12 : Illustration of a stylus including a spring-loaded stylus terminal for activating a switch. Detailed description

[0048] Turning now to a more detailed description and with reference to the accompanying drawings, the prior art Figure 1 Reference numerals will be used to refer to identical parts throughout the several views. Unless expressly so identified, nothing in the following description should be construed as an admission of prior art. Figure 3 The present disclosure is characterized by a stylus 60 and a liquid crystal writing device 70, which includes a liquid crystal writing element 10 that is erased by the stylus. The liquid crystal writing element 10 includes a liquid crystal layer 4, which includes a cholesteric liquid crystal material. The cholesteric liquid crystal material includes a cholesteric liquid crystal with optional spacers that affect the thickness of the liquid crystal layer and the sensitivity of the liquid crystal layer to pressure. Specifically, the cholesteric liquid crystal material includes a dispersion of cholesteric liquid crystal and a polymer to control pressure sensitivity. The liquid crystal layer 4 is very thin, for example, with a thickness of approximately 2 microns to 10 microns. The flexible transparent substrate 6 has a writing surface W, on which a user applies pressure that compresses the liquid crystal, which in turn changes the reflectivity of the cholesteric liquid crystal to form at least one image on the writing element 10. The reflectivity of the liquid crystal layer 4 can be changed from a light-scattering (substantially transparent) texture to a colored reflective texture (U.S. Patent No. 6,104,448), or from a colored reflective texture to a transparent texture (U.S. Patent Application No. 17 / 321,792, incorporated by reference), depending on the cholesteric liquid crystal material and the thickness of the liquid crystal layer 4. These changes in reflectivity can occur without applying a voltage.

[0049] While not wishing to be bound by theory, for example, the application of pressure can cause the liquid crystal to flow, thereby changing the reflectivity of the liquid crystal. Conductive layers 3 and 5 are present, with the liquid crystal layer 4 disposed between the conductive layers 3 and 5. The front conductive layer 5 and the front substrate 6 are transparent, while the rear conductive layer 3 and the rear substrate 2 can be transparent, opaque, or translucent. Based on this disclosure, one of ordinary skill in the art will understand that if a substrate or conductive layer is indicated as transparent or clear, this does not require a specific level of optical transparency, only that the substrate or conductive layer be transparent to the naked eye. If a spacer is used, it is disposed between the conductive layers. The conductive layers 5 and 3 are disposed between the front substrate 6 and the rear substrate 2. It should be understood that the dimensions of the components of the liquid crystal writing element 10 shown in the figures are not to scale. Furthermore, the conductive layer need not physically contact the liquid crystal layer or substrate, i.e., an intermediate layer or intermediate material may optionally be used between the substrate and the conductive layer, and between the conductive layer and the liquid crystal layer. Respectively, the front protrusion 7 is formed from the front substrate to expose the front conductive layer, and the rear protrusion 8 is formed from the rear substrate to expose the rear conductive layer ( Figure 5 ). The writing device 70 includes a housing 71. Figure 3 , the writing device terminal 72 is exposed from the housing 71 and is conductive. The writing device terminal 72 is electrically connected to the conductive layers 3 and 5 exposed on the protrusions 7 and 8 ( Figure 5 Stylus 60 includes stylus electronics 64 powered by power supply 63 to apply an erase voltage, such as an erase voltage waveform, to stylus terminal 62 of the stylus and to writing device terminal 72 that erases at least one image on the writing device.

[0050] The application of pressure from the stylus on the writing surface W enables the cholesteric liquid crystal material to be placed into a reflective state (called a planar texture) in a localized area that approximates the size of the stylus and the distance traveled by the moving stylus. In one example, the liquid crystal material is erased to a substantially transparent state (called a focal conic texture). The optional light absorbing layer 1 or light absorbing back surface at least partially absorbs light that passes through the liquid crystal layer and can be opaque or translucent. The light reflective writing or marking is in a reflective planar texture while the background is in a substantially transparent focal conic texture that enables the light absorbing layer or light absorbing back surface to be seen (in the direction of the observer V). The light absorbing layer or light absorbing back surface 1 provides contrast to the reflective writing on the liquid crystal writing element 10 so that when the light is reflected along the liquid crystal writing element 10, the light absorbing layer or light absorbing back surface 1 can be seen. Figure 1 When viewed along the direction of the observer V, at least one image can be observed on the liquid crystal element 10 .

[0051] like Figure 3As shown, stylus 60 is used not only to write on writing element 10 but also to erase written images. Stylus 60 can function similarly to a conventional pencil, with an optional writing tip 61 at one end for applying pressure to a localized or different area of the substrate and affecting the width of the written line. The stylus includes stylus electronics 64, a power source 63, and stylus terminals 62 at the opposite end of the stylus. Stylus tip 61 forms a dot or other shape and applies pressure to writing surface W of liquid crystal writing element 10, thereby forming writing and at least one image on liquid crystal writing element 10. No aspect of the present disclosure requires that the stylus tip leave a substance, such as paint or ink, on the writing surface, and in certain aspects of the present disclosure, the writing tip does not leave such printed substances during writing. The shape and size of the stylus tip affect the width of the written line. Writing with pen tip 61 is optional, as it is known in the art that one can write on writing element 10 with a fingernail or a pointed object that can apply localized pressure to the surface of writing element 10 (including any portion of a stylus that can apply localized pressure). In the disclosed writing device, stylus electronics 64 also include unique intelligent features such that when stylus terminals 62 make electrical contact with writing device terminals 72, the electrical contact is automatically detected by stylus electronics 64, and an erase voltage or erase voltage waveform is generated and applied to the conductive layer of the liquid crystal writing element, thereby enabling the liquid crystal material to be erased or otherwise cleared of writing and at least one image on liquid crystal writing element 10. Writing device 70 may include a flexible writing surface W and writing element 10 mounted in a housing 71. For example, housing 71 may form a frame surrounding writing element 10.

[0052] Alternatively, one could replace the smart electronic feature with a switch 65 that could be operated by a button so that a user could manually apply an erase voltage waveform to erase or clear writing from at least one image. Figure 10 and Figure 11 An example of a stylus including a switch 65 with a button and associated electronic circuitry is shown in FIG.

[0053] exist Figure 10 and Figure 12 In another variation shown, one can replace the smart electronic feature with a spring-activated switch 83 and associated electronic circuitry. One of the stylus terminals 62 is spring-loaded, and when compressed, the spring-activated switch 83 is activated, causing pressing the stylus against the writing device terminal to apply an erase voltage waveform to erase or clear writing from at least one image.

[0054] The components of one embodiment of the stylus 60 are Figure 3, includes a power source 63, which may be a battery or a photovoltaic or other device for generating electricity. The battery may be replaceable, or may not be replaceable because the power consumption is so small that it can meet the life of the stylus. The unique stylus electronics 64 will be described in detail later in this document. One or more of the stylus terminals 62 may optionally be spring biased (e.g., spring loaded) to ensure better electrical contact with the writing device terminals 72 and provide a suitable touch feel for the user. An optional pen tip 61 is mounted on the stylus and supported by the stylus. The pen tip 61 is typically in the form of a pointed object, but can be any other shape to provide a local pressure for writing on the writing surface W of the flexible substrate 6, which causes the reflectivity of the cholesteric liquid crystal material to display an image on the writing surface W.

[0055] Electrically connected to at least two stylus terminals 62. Figure 4A and Figure 4B Two examples of stylus terminal configurations are shown in , although other terminal configurations are possible. Figure 4A The stylus terminals 62a and 62b in FIG are terminal configurations used in examples described later, wherein the stylus terminal 62b is optionally spring-loaded for improving the reliability of the electrical connection with the writing device terminal 72b. When the stylus terminal 62b and the writing device terminal 72b are electrically engaged, the stylus terminal 62a is electrically connected to the writing device terminal 72a to complete the circuit for erasing the writing device. Figure 4B , wherein stylus terminal 62c is optionally spring-loaded and stylus terminal 62d may or may not be spring-loaded. In this configuration, stylus terminal 62c is electrically connected to writing device terminal 72c, and stylus terminal 62d is electrically connected to writing device terminal 72d to complete the circuit for erasing writing on the writing surface of writing element 10. It should be understood that the electrical contact or electrical engagement between the terminals may or may not be physical contact. It should also be understood that the use of spring-loaded terminals does not require the use of a spring-activated switch 83 that operates in conjunction with the spring-loaded stylus terminals.

[0056] The stylus terminal 62 and the writing device terminal 72 can be other shapes or combinations understood by those of ordinary skill in the art in light of the present disclosure. For example, the circular terminal on the stylus 60 or on the writing device housing 71 can be configured as a semicircle or other segment of a circle. In addition, the annular stylus terminal or writing device terminal can be replaced by one or more segments of a ring. The terminals can take other shapes, including but not limited to squares, rectangles, triangles, hexagons or other polygons, or parts of these shapes. The terminals can even take more complex shapes. According to the present disclosure, those of ordinary skill in the art will understand that the number, shape, configuration and arrangement of the terminals and the shape and configuration of the stylus should not be used to unduly limit the present disclosure or support assertions that are not within the scope of the present disclosure. There can also be a guide on the stylus and / or on the writing device housing (not shown in FIG. 4 ) to guide the stylus for making a reliable electrical connection. For example, the housing can include an annular ridge surrounding the external writing device terminal that enables the erasing end of the stylus to be received so that the terminals are precisely aligned and engaged.

[0057] Figure 5 The internal components of the writing device 70 are shown, which are contained by the housing 71. The liquid crystal writing element 10 includes Figure 1 The housing 71 also supports writing device terminals 72a, 72b which have electrical connections to the conductive layers 3 and 5 (not shown) on the protrusions 7 and 8 of the liquid crystal writing element 10 (all of which can be hidden inside the housing). Figure 5 As shown, one portion of the circuit from the conductive layer on projection 7 is located at or near writing device terminal 72a, while another portion of the circuit from the conductive layer on projection 8 is located at or near writing device terminal 72b. Writing device terminals 72a and 72b are spaced apart from each other to avoid a short circuit between them. In addition, resistor 80 may optionally be connected between writing device terminals 72a and 72b. Resistor 80 may be used for a number of purposes, including Figure 3 Stylus electronics 64 can automatically detect contact between stylus terminal 62 and writing device terminal 72 and apply the erase voltage waveform without further action by the user. Connection can also be detected by using the capacitance of the display or an additional connection. Other possible functions of resistor 80 may include discharging the display, which may occur, for example, if the stylus is removed prematurely, as described in the next paragraph.

[0058] Voltage waveforms for erasing writing devices are described in US Patent No. 10,558,065, which is incorporated herein by reference in its entirety. The stylus may use any waveform known in the art. Figure 6The most common waveforms that can be used by a stylus are shown in , which shows two voltage waveforms VA and VB that are to be applied to the writing device terminals 72a and 72b, respectively, in order to erase the liquid crystal writing element 10 by driving it to a dark focal conic background. The drive waveforms VA and VB include 3 levels: 0V, VFC, and VP. Although each of these levels is either zero or positive, the composite voltage waveform (VA-VB) seen on the display is bipolar and consists of the levels 0V, ±VFC, and ±VP. The typical duration of the pulses (positive or negative) in the composite waveform is 150 milliseconds (ms). The ±VP pulses drive the liquid crystal to a homeotropic state that eliminates the distorted cholesteric phase structure and clears the previous image. As Figure 6 As shown, these pulses are followed by a lower voltage level pulse, VFC, of alternating polarity, which drives the writing device to the focal conic texture and erases the image. Alternating polarity pulses are necessary to avoid ionic conductivity damage to the writing device. If complete erasure is not desired, the waveform may not require the voltage pulse, VP. However, the initial VP pulse is advantageous for better erasure and to avoid ghosting.

[0059] Another voltage waveform called a slow discharge erase waveform is disclosed in U.S. Patent No. 10,558,065 (which is incorporated herein by reference), and is applied for a portion to drive the cholesteric liquid crystal to an isotropic texture to erase the image, followed by a slow decay portion in which the charge on the writing device is discharged, thereby driving the writing device to a focal conic texture. Any erase waveform can be applied by the electronics of the stylus. Example 1, which will be described later, uses a slow discharge erase waveform. This waveform is applied to the stylus. Figure 7 As shown in Figure 7 Two voltage waveforms VA and VB are shown which are to be applied to the writing device terminals 72a and 72b respectively to drive the writing device to the isotropic texture and erase the previous image as described above. In order to leave the writing device in the dark focal conic texture and erase the writing device, a slow discharge of the writing device is followed by a ±VP (voltage plane) pulse. This will initialize the writing device for the next image. The slow discharge portion of the waveform causes the voltage to drop from VP to 0V. The initial polarity of the waveform may be alternated to avoid ion migration in the liquid crystal material which would limit the life of the writing device. The duration of the slow discharge may be controlled by the erase circuit of the stylus or by the value RC, where R is the effective resistance and C is the effective capacitance C between the disconnected terminals 72a and 72b of the writing device. In Example 1, the slow discharge portion is controlled by Figure 5The value of resistor 80 is controlled by the effective capacitance of the liquid crystal layer of writing surface element 10. The value of RC is sufficient to ensure that all areas of the writing device switch directly to the focal conic texture for display uniformity. The duration of the slow discharge portion is at least 10 milliseconds but can be as long as several seconds. Typical values are similar to those used in the examples described later. If the resistivity or effective resistance of liquid crystal writing element 10 is low enough to discharge the capacitance of the writing device, resistor R is not required.

[0060] Figure 8 A schematic representation of a stylus detection and erase circuit 200 is provided for detecting the presence of an electrical connection to a writing device and erasing the stylus. Figure 7 The waveform is driven to the stylus terminals 62a and 62b. The drive circuit is first described. A high-side driver 250 is provided to connect the stylus terminals 62a and 62b to the voltage source 240. A low-side driver 260 is provided to ground the stylus terminals 62a and 62b. A current limiting resistor 230 (optional) is included between the stylus terminals 62a and 62b and the drivers 250 and 260. The control signals 270 to 273 are sequenced to enable the driver to generate the required drive waveform at the stylus terminals 62a and 62b / prohibit the driver from generating the required drive waveform at the stylus terminals 62a and 62b. In coordination, the voltage source 240 is configured to output VP. The control logic and implementation of the voltage source 240 for sequencing the control signals 270 to 273 are known in the art and include the stylus electronics 64 together with the detection and drive circuit 200. The optional detection circuit described next includes resistor 231 , diode 280 , and nodes 210 and 211 .

[0061] In certain aspects of the present disclosure, the control logic of stylus electronics 64 implements a low-power mode that is capable of detecting contact between stylus terminal 62 and writing device terminal 72. An erase waveform is automatically applied when contact is detected without requiring further action by the user, such as pressing a switch. Figure 8This functionality is supported by detection and drive circuitry 200. In low-power detection mode, control signal 273 is asserted, grounding stylus terminal 62b via optional resistor 230, and a voltage (e.g., logic power supply VDD for the stylus electronics) is applied to node 210. The voltage at node 211 is monitored for a logic-low value, for example, using a microcontroller's digital I / O interrupt. In the absence of a connection to the stylus terminal, node 211 will read as a logic-high value due to the pull-up provided by resistor 231 on the voltage applied to node 210. When stylus terminal 62 is connected to writing device terminal 72, node 211 will be temporarily pulled to a logic-low value by diode 280 due to the discharged capacitance of liquid crystal writing element 10. Resistor 80 also facilitates this detection, pulling node 211 low via the voltage divider formed by resistor 231. After electrical contact between stylus 60 and liquid crystal writing element 10 is detected, node 210 is set to ground when generating the erase waveform. Diode 280 protects the control circuitry connected to nodes 210 and 211 from the high voltage applied to terminal 62a during the erase process.

[0062] Other aspects of the present disclosure use manual erasure whereby a switch (e.g., push button switch 65 or spring activated switch 83) can apply a voltage waveform to erase the image. In this case, for example, the image can be removed. Figure 8 detection circuit and switches the switch 65 or the spring activated switch 83 to Figure 10 The switch 65 may include a Figure 11 The buttons on the stylus as shown and Figure 10 The erase electronic device 66 is shown. In another feature, the spring activated switch 83 can be used to include Figure 12 The spring loaded stylus terminal 62 shown and the Figure 10 Shown are erase electronics 66. Depressing button 65 or spring loaded stylus terminal 62 and closing the switch applies an erase waveform to stylus terminal 62 and when terminal 62 makes electrical contact with terminal 72 of the writing device, the erase waveform is applied to erase the image.

[0063] This disclosure will now provide examples of specific features, which should not be used to unduly limit the claimed subject matter.

[0064] Example

[0065] As an example, Figure 3 The working stylus 60 is made of an erasing stylus terminal, which is as shown in FIG. Figure 4A 62a and 62b are shown for erasing Figure 5The central stylus terminal 62b is spring loaded to ensure good contact with the writing device terminal. Figure 8 The detection and driving circuit 200 in.

[0066] The stylus electronic device also includes Figure 9 The particular circuit 300 shown thereby provides an embodiment of the control logic and voltage source 240 as part of the stylus circuit 64 and the power supply 63 . Figure 9 The microprocessor 290 is a Texas Instruments MSP430F2001, and the power supply 63 is composed of two LR44 batteries connected in series, with an output of 3V. The resistor 80 between the terminals of the writing element 10 has a resistance of 200 kilo-ohms (kΩ). The microcontroller 290 executes the control signals 270-273 and the writing device detection signals 210 and 211. Figure 8 The microcontroller 290 further controls the boost converter 265 to generate a voltage of VP at the voltage source 240. The microcontroller 290 senses the voltage source 240 via a signal 275. If the voltage at the voltage source 240 is less than the VP voltage, the microcontroller 290 provides a PWM signal to the boost converter input 274 until the voltage at the voltage source 240 is greater than or equal to VP.

[0067] By using the commercial Jot8.5 Boogie from Kent Display Writing device, a cholesteric liquid crystal writing device that can be erased with a stylus was developed. In this model, the erasing electronics and erase button were removed, and the Figure 5 The writing device terminals of the design shown in 72a and 72b are added to the area of the removed buttons. Figure 1 and Figure 5 As shown, writing device terminals 72a and 72b are connected to conductive layers or electrodes 3 and 5 on protrusions 7 and 8, respectively. For compatibility with the prototype stylus electronics, a resistor (e.g., Figure 5 80 in FIG), with a resistance value of 200 kΩ. When the stylus terminals were placed in contact with the writing device terminals, the stylus was observed to erase the written image on the writing device. Furthermore, it was observed that the writing device could be completely erased even if the stylus was removed before the erasure was fully completed, which is a unique property of the specific electronic device and waveform selected for this example.

[0068] Many modifications and variations of the subject matter of the present disclosure will be apparent to those skilled in the art.It is therefore to be understood that the subject matter of the present disclosure can be implemented in other ways than those specifically shown and described.

[0069] Furthermore, the present disclosure provides the following items.

[0070] 1. A stylus pen and a liquid crystal writing device, wherein the liquid crystal writing device is erased by the stylus pen, and the liquid crystal writing device comprises:

[0071] a liquid crystal layer comprising a cholesteric liquid crystal material,

[0072] a flexible surface on which a user applies pressure, said pressure changing the reflectivity of said cholesteric liquid crystal material to form an image on said writing device,

[0073] conductive layers, the liquid crystal layer being disposed between the conductive layers,

[0074] a writing instrument terminal, the writing instrument terminal being conductive and connected to the conductive layer; and

[0075] The stylus pen comprises:

[0076] Stylus electronics are adapted to apply an erase voltage to the writing device terminals.

[0077] 2. The stylus and liquid crystal writing device of item 1, wherein the stylus electronics are adapted to detect electrical contact with the writing device terminals and automatically apply the erase voltage to the writing device terminals.

[0078] 3. The stylus and liquid crystal writing device of item 2, wherein the stylus comprises a power source and the stylus electronics, and wherein an optional resistor is connected between the writing device terminals.

[0079] 4. The stylus pen and liquid crystal writing device according to item 3, wherein the stylus pen includes a writing tip.

[0080] 5. The stylus and liquid crystal writing device of item 1, the stylus comprising a switch, wherein the stylus electronics are adapted to apply the erase voltage to the writing device terminals when activated by the switch.

[0081] 6. The stylus pen and liquid crystal writing device according to item 5, wherein the stylus pen includes a button that activates the switch when pressed.

[0082] 7. A stylus and liquid crystal writing device according to item 5, wherein the stylus includes a stylus terminal that is spring-loaded and engages one of the writing device terminals, wherein when the spring is compressed, the spring-loaded stylus terminal activates the switch.

[0083] 8. The stylus pen and liquid crystal writing device according to item 1, wherein the cholesteric liquid crystal material comprises a dispersion of cholesteric liquid crystal and a polymer, and includes a spacer.

[0084] 9. The stylus and liquid crystal writing device of item 1, wherein the erase voltage is an erase portion of a slow discharge waveform, and the stylus electronics are adapted to apply the erase portion of the slow discharge waveform to the writing device terminals.

[0085] 10. The stylus pen and liquid crystal writing device of item 9, wherein the writing device is adapted to apply the discharge portion of the slow discharge waveform such that the slow discharge waveform erases at least one of the images.

[0086] 11. The stylus pen and liquid crystal writing device according to item 9, wherein the liquid crystal writing device includes a resistor having a resistance value and connected between terminals of the writing device.

[0087] 12. The stylus pen and liquid crystal writing device of item 11, wherein the product of the resistance value and the effective capacitance of the liquid crystal layer produces a value of a discharge time that causes at least one of the images to be erased.

[0088] 13. The stylus pen and liquid crystal writing device of item 9, wherein the effective resistance of the liquid crystal layer causes discharge and erasure of at least one of the images.

[0089] 14. The stylus pen and liquid crystal writing device of item 13, wherein the product of the effective resistance and effective capacitance of the liquid crystal layer produces a value of discharge time that causes at least one of the images to be erased.

[0090] 15. The stylus pen and liquid crystal writing device according to item 1, wherein the stylus pen comprises:

[0091] a stylus terminal that is electrically conductive and adapted to engage the writing device terminal, and

[0092] The stylus terminal includes a first stylus terminal and a second stylus terminal separated from the first stylus terminal.

[0093] 16. The stylus pen and liquid crystal writing device according to item 15, wherein the first stylus terminal has a circular shape or a shape having a portion of a circle.

[0094] 17. The stylus pen and liquid crystal writing device according to item 15, wherein the second stylus terminal includes a ring shape or a shape having a portion of a ring.

[0095] 18. The stylus pen and liquid crystal writing device according to item 15, wherein the first stylus terminal includes a circular protrusion, and the second stylus terminal includes a ring, the circular protrusion being located inside the ring.

[0096] 19. The stylus pen and liquid crystal writing device according to item 1, comprising:

[0097] case;

[0098] wherein the liquid crystal layer and the conductive layer are contained in the housing, and the housing forms a frame around the flexible surface; and

[0099] The writing device terminal is arranged on the outer surface of the housing.

[0100] 20. The stylus pen and liquid crystal writing device according to item 1, wherein the erase voltage comprises an erase voltage waveform.

[0101] 21. A stylus pen for erasing a liquid crystal writing device, comprising:

[0102] a battery, the battery being disposed inside the stylus;

[0103] an erasing electronic device, the erasing electronic device being disposed inside the stylus and powered by the battery, the erasing electronic device being adapted to generate an erasing voltage; and

[0104] conductive stylus terminals;

[0105] The erase electronics are adapted to detect electrical contact with writing device terminals of the liquid crystal writing device and automatically apply the erase voltage to the writing device terminals.

[0106] 22. The stylus of item 21, wherein the erase voltage is an erase portion of a slow-discharge waveform, the stylus electronics being adapted to apply the erase portion of the slow-discharge waveform to the writing device terminals.

Claims

1. An assembly comprising a stylus and a liquid crystal writing device, the liquid crystal writing device being erased by the stylus, The liquid crystal writing device comprises: a liquid crystal layer comprising a cholesteric liquid crystal material, a flexible surface on which a user applies pressure, said pressure changing the reflectivity of said cholesteric liquid crystal material to form an image on said writing device, conductive layers, the liquid crystal layer being disposed between the conductive layers, a writing instrument terminal, the writing instrument terminal being conductive and connected to the conductive layer, the writing instrument terminal including two terminals spaced apart from each other; The writing device terminal is provided on an outer surface of the writing device; and the stylus comprises: stylus electronics, the stylus electronics being part of the stylus, the stylus electronics including conductive stylus terminals, wherein the stylus terminals are configured to make electrical contact with the writing device terminals, whereby the stylus electronics applies an erase voltage to the writing device terminals, the erase voltage completely erasing an entire image formed on the writing device; wherein the stylus includes a writing tip located on one end of the stylus, and the stylus terminal is located on an opposite end of the stylus; Wherein, the stylus terminal is provided on the outer surface of the stylus; The stylus terminal includes a first stylus terminal and a second stylus terminal separated from the first stylus terminal.

2. The assembly according to claim 1, wherein The stylus electronics detect when the stylus terminals are brought into electrical contact with the writing device terminals and automatically apply the erase voltage to the writing device terminals.

3. The assembly according to claim 2, wherein The stylus includes a power source, and wherein a resistor is connected between the writing device terminals.

4. The assembly of claim 1 , the stylus comprising a switch, wherein: The stylus electronics apply the erase voltage to the writing device terminals when activated by the switch.

5. The assembly according to claim 4, wherein The stylus includes a button that activates the switch when pressed.

6. The assembly according to claim 4, wherein The stylus terminal includes a spring-loaded stylus terminal that engages one of the writing device terminals, wherein the spring-loaded stylus terminal activates the switch when the spring is compressed.

7. The assembly according to claim 1, wherein The cholesteric liquid crystal material includes a dispersion of cholesteric liquid crystal and a polymer, and includes a spacer.

8. The assembly of claim 1, wherein: The erase voltage is an erase portion of a slow-discharge waveform, and the stylus electronics applies the erase portion of the slow-discharge waveform to the writing device terminals.

9. The assembly according to claim 8, wherein The writing device is adapted to apply the discharge portion of the slow-discharge waveform such that the slow-discharge waveform results in the complete erasure of the entire image.

10. The assembly according to claim 8, wherein The liquid crystal writing device includes a resistor having a resistance value and connected between terminals of the writing device.

11. The assembly according to claim 10, wherein The product of the resistance value and the effective capacitance of the liquid crystal layer yields a value of discharge time that results in the complete erasure of the entire image.

12. The assembly of claim 8, wherein The effective resistance of the liquid crystal layer results in the discharge and the complete erasure of the entire image.

13. The assembly of claim 12, wherein: The product of the effective resistance and effective capacitance of the liquid crystal layer yields a value of discharge time that results in the complete erasure of the entire image.

14. The assembly of claim 1, wherein: The first stylus terminal has a circular shape or a shape having a portion of a circle.

15. The assembly of claim 1, wherein The second stylus terminal includes a ring shape or a shape having a portion of a ring.

16. The assembly of claim 1, wherein The first stylus terminal includes a circular protrusion, and the second stylus terminal includes a ring, the circular protrusion being located inside the ring.

17. The assembly of claim 1, comprising: case; The writing device terminal is arranged on the outer surface of the housing.

18. The assembly of claim 1, wherein The erase voltage includes an erase voltage waveform.

19. A stylus pen for erasing a liquid crystal writing device, comprising: a battery, the battery being disposed inside the stylus; an erasing electronic device, the erasing electronic device being disposed inside the stylus and powered by the battery, the erasing electronic device generating an erasing voltage; as well as conductive stylus terminals; wherein the erasing electronics detects when the stylus terminal is brought into electrical contact with a writing device terminal of the liquid crystal writing device and automatically applies the erasing voltage to the writing device terminal, the erasing voltage completely erasing the entire image formed on the writing device; wherein the stylus includes a writing tip located on one end of the stylus, and the stylus terminal is located on an opposite end of the stylus; Wherein, the stylus terminal is provided on the outer surface of the stylus; The stylus terminal includes a first stylus terminal and a second stylus terminal separated from the first stylus terminal.

20. The stylus pen according to claim 19, wherein The erase voltage is an erase portion of a slow discharge waveform, and the erase electronics are adapted to apply the erase portion of the slow discharge waveform to the writing device terminals.

Images