Liquid crystal handwriting board, control method thereof, and handwriting device

Abstract

A liquid crystal handwriting board, a control method thereof and a handwriting device. The liquid crystal handwriting board comprises a liquid crystal panel and a driving assembly electrically connected with the liquid crystal panel. The liquid crystal panel comprises a first substrate and a second substrate arranged oppositely, and a liquid crystal layer between the first substrate and the second substrate. The first substrate comprises a plurality of pixel electrodes and a plurality of photosensitive devices electrically connected with the plurality of pixel electrodes. The second substrate comprises a planar common electrode. The driving assembly is configured to provide a control voltage to a control electrode of the plurality of photosensitive devices, and provide a pixel voltage to a first electrode of the plurality of photosensitive devices, so that the photosensitive devices in a to-be-erased area are turned on. The to-be-erased area is an area receiving light with a first intensity. A voltage difference is formed between the pixel electrodes in the to-be-erased area and the common electrode. The present disclosure realizes local area erasing of the liquid crystal handwriting board by light, and the area not illuminated will not be affected, and no positioning device is needed.

Description

Technical Field

[0001] This disclosure relates to, but is not limited to, the field of display technology, and in particular to a liquid crystal handwriting tablet and its control method and handwriting device. Background Technology

[0002] A handwriting tablet is an electronic device used for writing and drawing. Among them, LCD handwriting tablets have the advantages of low power consumption and clear handwriting, and have gained a significant market share in recent years. However, most LCD handwriting tablets currently only allow for full-screen erasure, resulting in limited flexibility.

[0003] Among LCD handwriting tablets capable of partial erasure, some achieve this through a combination of voltage control by a driving circuit and a positioning device. This method typically results in imprecise erasure boundaries, is prone to accidental erasures, and consumes more power, undoubtedly increasing equipment costs and reducing reliability. Other LCD handwriting tablets achieve partial erasure through illumination. This method reduces equipment costs, but during the erasure process, the handwriting information in non-illuminated areas gradually fades over time, severely impacting the user experience. Summary of the Invention

[0004] This disclosure provides a liquid crystal writing tablet and its control method and writing device, which can erase local areas through illumination, while non-illuminated areas are not affected, and no positioning device is required.

[0005] This disclosure provides a liquid crystal writing tablet, including a liquid crystal panel and a driving assembly electrically connected to the liquid crystal panel. The liquid crystal panel includes a first substrate and a second substrate disposed opposite to each other, and a liquid crystal layer located between the first substrate and the second substrate. The first substrate includes a plurality of pixel electrodes and a plurality of photosensitive devices electrically connected to the plurality of pixel electrodes. The second substrate includes a planar common electrode. The driving assembly is configured to provide a control voltage to the control electrode of the plurality of photosensitive devices and a pixel voltage to the first electrode of the plurality of photosensitive devices, thereby turning on the photosensitive devices in an area to be erased. The area to be erased is a region receiving light with an illumination intensity of a first intensity, and a voltage difference is formed between the pixel electrodes in the area to be erased and the common electrode.

[0006] In some exemplary embodiments, the photosensitive device is a phototransistor, and the first substrate further includes multiple scan signal lines and multiple data signal lines, the multiple scan signal lines extending in a first direction, the multiple data signal lines extending in a second direction, and the first direction and the second direction intersecting.

[0007] The gate electrode of the phototransistor is connected to the scan signal line, the first electrode of the phototransistor is electrically connected to the data signal line, and the second electrode of the phototransistor is electrically connected to the pixel electrode. The phototransistor is turned on under the combined control of the control voltage, the pixel voltage, and the light of the first intensity.

[0008] In some exemplary embodiments, the control voltage is between -5V and -2V, the pixel voltage is between 10V and 60V, and the first intensity is between 20,000 and 40,000 nits.

[0009] In some exemplary embodiments, the control voltage is between -2V and 5V, the pixel voltage is between 20V and 40V, and the first intensity is between 5000 and 20000 nits.

[0010] In some exemplary embodiments, the first electrode of the phototransistor includes a U-shaped structure, the second electrode of the phototransistor includes a strip-shaped structure, one end of the second electrode is located within the U-shaped structure, and the other end of the second electrode is electrically connected to the pixel electrode.

[0011] In some exemplary embodiments, the first substrate includes a first substrate, a gate layer disposed on the first substrate, a gate insulating layer disposed on the gate layer, a semiconductor layer disposed on the gate insulating layer, a source / drain electrode layer disposed on the semiconductor layer, a passivation layer disposed on the source / drain electrode layer, and a first planarization layer disposed on the passivation layer.

[0012] The scanning signal line, the gate electrode of the phototransistor, and the gate layer are disposed on the same layer.

[0013] The data signal line, the first and second electrodes of the phototransistor, and the source / drain electrode layer are disposed on the same layer.

[0014] In some exemplary embodiments, the semiconductor layer includes an active layer and an ohmic contact layer disposed on the active layer, the active layer being electrically connected to the first electrode and the second electrode through the ohmic contact layer.

[0015] In some exemplary embodiments, the active layer includes a channel region having a width of 45 to 55 micrometers and a length of 4 to 6 micrometers.

[0016] In some exemplary embodiments, the active layer is made of amorphous silicon and has a thickness of 1,500 to 2,100 angstroms.

[0017] This disclosure also provides a display device, including: a liquid crystal writing tablet as described above, and an erasing tool, the erasing tool including an emitting light source and a control switch, the control switch being used to control the emitting light source to be turned on or off.

[0018] In some exemplary embodiments, the handwriting device further includes a switch electrically connected to the driving component, wherein: when the switch is turned on, the driving component provides a first range of control voltage to the control electrode of the plurality of photosensitive devices and a second range of pixel voltage to the first electrode of the plurality of photosensitive devices.

[0019] This disclosure also provides a method for manufacturing a liquid crystal writing tablet, the liquid crystal writing tablet including a liquid crystal panel and a driving component electrically connected to the liquid crystal panel; the liquid crystal panel includes a first substrate and a second substrate disposed opposite to each other, and a liquid crystal layer located between the first substrate and the second substrate, the first substrate including: a plurality of pixel electrodes and a plurality of photosensitive devices electrically connected to the plurality of pixel electrodes; the second substrate including a planar common electrode; the control method includes: the driving component providing a control voltage to the control electrode of the plurality of photosensitive devices and providing a pixel voltage to the first electrode of the plurality of photosensitive devices; the area to be erased receiving light with an illumination intensity of a first intensity, the photosensitive device in the area to be erased being turned on; a voltage difference being formed between the pixel electrode and the common electrode in the area to be erased, and the liquid crystal molecules located in the area to be erased rearranging under the action of the voltage difference.

[0020] The liquid crystal writing tablet and its control method and writing device of this disclosure, by setting a photosensitive device, can only be activated under the combined control of a certain intensity of control voltage, pixel voltage and illumination, thereby realizing the erasure of local areas of the liquid crystal writing tablet by illumination, while non-illuminated areas are unaffected. Furthermore, the liquid crystal writing tablet of this disclosure does not require the cooperation of a positioning device, simplifying the driving circuit and reducing equipment costs. In addition, the manufacturing process of this disclosure is well compatible with existing manufacturing processes, is simple to implement, easy to carry out, has high production efficiency, low production cost and high yield.

[0021] Other features and advantages of this disclosure will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the disclosure. Other advantages of this disclosure may be realized and obtained by means of the methods described in the description and the accompanying drawings. Attached Figure Description

[0022] The accompanying drawings are used to provide an understanding of the technical solutions of this disclosure and form part of the specification. They are used together with the embodiments of this disclosure to explain the technical solutions of this disclosure and do not constitute a limitation on the technical solutions of this disclosure.

[0023] Figure 1 This is a schematic diagram of the structure of a liquid crystal handwriting tablet provided in an embodiment of this disclosure;

[0024] Figure 2 This is a schematic diagram of the film layer structure of a liquid crystal panel in a liquid crystal handwriting tablet provided in this embodiment of the present disclosure;

[0025] Figure 3 yes Figure 2 The image shows a top view of the liquid crystal panel in the phototransistor region of the liquid crystal writing tablet.

[0026] Figure 4 yes Figure 2 A top view of the phototransistor shown;

[0027] Figure 5 A schematic diagram of photosensitive transistor test results as drain voltage changes, which is an exemplary embodiment of the present disclosure;

[0028] Figure 6 This is a schematic diagram of the photosensitive transistor's photosensitive test results as the brightness of the light source changes, which is an exemplary embodiment of the present disclosure.

[0029] Figure 7 This is a schematic diagram of the photosensitive transistor as a function of gate voltage, representing an exemplary embodiment of the present disclosure.

[0030] Figure 8 This is a schematic diagram of the working timing of a liquid crystal handwriting tablet, which is an exemplary embodiment of the present disclosure.

[0031] Figure 9 A schematic diagram illustrating the working timing of another liquid crystal handwriting tablet as an exemplary embodiment of this disclosure;

[0032] Figure 10 yes Figure 2 A top view of the LCD panel in the LCD handwriting tablet shown;

[0033] Figure 11 This is a schematic diagram of the film structure of the liquid crystal panel in another liquid crystal handwriting tablet provided in this embodiment of the present disclosure;

[0034] Figure 12 yes Figure 11 A top view of the LCD panel in the LCD handwriting tablet shown;

[0035] Figure 13 This is a schematic diagram of the film layer structure of the liquid crystal panel in another liquid crystal handwriting tablet provided in this disclosure embodiment;

[0036] Figure 14 This is a schematic diagram of the structure of a handwriting device provided in an embodiment of this disclosure;

[0037] Figure 15 This is a schematic diagram of another handwriting device provided in an embodiment of this disclosure. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this disclosure clearer, embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. Note that the implementation methods can be carried out in many different forms. Those skilled in the art will readily understand that the methods and content can be varied in various forms without departing from the spirit and scope of this disclosure. Therefore, this disclosure should not be construed as limited to the content described in the following embodiments. Without conflict, the embodiments and features in the embodiments of this disclosure can be arbitrarily combined with each other.

[0039] In the accompanying drawings, the size of the constituent elements, the thickness of the layers, or the area are sometimes exaggerated for clarity. Therefore, one aspect of this disclosure is not necessarily limited to these dimensions, and the shapes and sizes of the components in the drawings do not reflect true proportions. Furthermore, the drawings schematically illustrate ideal examples, and one aspect of this disclosure is not limited to the shapes or values ​​shown in the drawings.

[0040] The ordinal numbers “first,” “second,” and “third” used in this specification are used to avoid confusion among the constituent elements, not to limit their quantity.

[0041] In this specification, for convenience, terms such as "middle," "upper," "lower," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer" are used to indicate orientation or positional relationships in conjunction with the accompanying drawings. This is solely for the purpose of facilitating the description and simplification, and does not imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this disclosure. The positional relationships of the constituent elements may be appropriately varied depending on the orientation of each constituent element being described. Therefore, the use of terms not limited to those described in the specification may be appropriately replaced as needed.

[0042] In this specification, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they may refer to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection, an indirect connection via an intermediate component, or a connection within two components. Those skilled in the art will understand the specific meaning of these terms in this disclosure based on the specific circumstances.

[0043] In this specification, a transistor is a device that includes at least three terminals: a gate electrode, a drain electrode, and a source electrode. A transistor has a channel region between the drain electrode (drain electrode terminal, drain region, or drain electrode) and the source electrode (source electrode terminal, source region, or source electrode), and current can flow through the drain electrode, the channel region, and the source electrode. Note that in this specification, the channel region refers to the region through which current primarily flows.

[0044] In this specification, the first electrode can be the drain electrode and the second electrode can be the source electrode, or vice versa. In cases where transistors with opposite polarities are used or the current direction changes during circuit operation, the functions of the "source electrode" and "drain electrode" may sometimes be interchanged. Therefore, in this specification, the "source electrode" and "drain electrode" can be interchanged.

[0045] In this specification, "electrical connection" includes the situation where components are connected together by elements that have a certain electrical function. There are no particular limitations on what constitutes an "electrical function," as long as it allows for the transmission and reception of electrical signals between the connected components. Examples of "electrical functions" include not only electrodes and wiring, but also switching elements such as transistors, resistors, inductors, capacitors, and other elements with various functions.

[0046] In this specification, "parallel" refers to the state where the angle formed by two straight lines is greater than or equal to -10° and less than 10°, and therefore also includes the state where the angle is greater than or equal to -5° and less than 5°. Similarly, "perpendicular" refers to the state where the angle formed by two straight lines is greater than or equal to 80° and less than 100°, and therefore also includes the state where the angle is greater than or equal to 85° and less than 95°.

[0047] In this specification, the terms "film" and "layer" may be interchanged. For example, "conductive layer" may sometimes be replaced with "conductive film." Similarly, "insulating film" may sometimes be replaced with "insulating layer."

[0048] In this disclosure, “about” means a value that is not strictly limited and allows for process and measurement errors.

[0049] This disclosure provides a liquid crystal handwriting tablet, including: a liquid crystal panel and a driving component electrically connected to the liquid crystal panel.

[0050] The liquid crystal panel includes a first substrate and a second substrate disposed opposite to each other, and a liquid crystal layer located between the first substrate and the second substrate. The first substrate includes a plurality of pixel electrodes and a plurality of photosensitive devices electrically connected to the plurality of pixel electrodes. The second substrate includes a planar common electrode.

[0051] The driving component is configured to: provide a control voltage to the control electrode of multiple photosensitive devices, provide a pixel voltage to the first electrode of multiple photosensitive devices, turn on the photosensitive devices in the area to be erased, the area to be erased is the area that receives light with an illumination intensity of a first intensity, and form a voltage difference between the pixel electrode and the common electrode in the area to be erased.

[0052] The liquid crystal handwriting tablet of this disclosure embodiment, by incorporating a photosensitive device, can only be activated under the combined control of a certain intensity of control voltage, pixel voltage, and illumination. This allows for the erasure of localized areas of the liquid crystal handwriting tablet through illumination, while unilluminated areas remain unaffected. Furthermore, the liquid crystal handwriting tablet of this disclosure embodiment does not require a positioning device, simplifying the driving circuitry and reducing equipment costs.

[0053] Figure 1 This is a schematic diagram of the structure of a liquid crystal handwriting tablet provided in an exemplary embodiment of the present disclosure. The liquid crystal handwriting tablet 000 may include: a liquid crystal panel 001 and a driving assembly 002.

[0054] The liquid crystal panel 001 may include: a first substrate 100 and a second substrate 200 disposed opposite to each other, and a liquid crystal layer 300 located between the first substrate 100 and the second substrate 200. The first substrate 100 may include: a plurality of pixel electrodes 101 and a plurality of photosensitive devices 102 electrically connected to the plurality of pixel electrodes 101. The second substrate 200 may include: a planar common electrode 201. For example, at least one pixel electrode 101 is block-shaped, the plurality of pixel electrodes 101 are arranged in a matrix, and the orthographic projection of the common electrode 201 on the first substrate 100 covers the area where the plurality of pixel electrodes 101 are located.

[0055] The driving component 002 is electrically connected to the liquid crystal panel 001. The driving component 002 is configured to: provide control voltage to the control electrode of the plurality of photosensitive devices 102 and provide pixel voltage to the first electrode of the plurality of photosensitive devices when the liquid crystal handwriting pad 000 is in the erasure mode, so that the photosensitive devices in the area to be erased are turned on. The area to be erased is the area that receives light with an illumination intensity of the first intensity. A voltage difference is formed between the pixel electrode 101 and the common electrode 201 in the area to be erased.

[0056] The liquid crystal writing tablet provided in this embodiment includes a liquid crystal panel and a driving assembly. The liquid crystal panel includes a first substrate and a second substrate disposed opposite to each other, and a liquid crystal layer located between the first substrate and the second substrate. Since the pixel electrodes in the first substrate of the liquid crystal panel are multiple block electrodes, when the liquid crystal writing tablet is in erase mode, the driving assembly electrically connected to the liquid crystal panel can provide control voltage to the control electrode of multiple photosensitive devices 102 and provide pixel voltage to the first electrode of multiple photosensitive devices, so that the photosensitive devices in the area to be erased are turned on. The area to be erased is the area that receives light with an illumination intensity of a first intensity, so that a voltage difference is formed between the pixel electrode and the common electrode in the area to be erased, thereby causing the liquid crystal molecules in the liquid crystal layer located in the area to be erased to rearrange under the action of the voltage difference. In this way, local area erasure of the liquid crystal writing tablet can be realized, improving the flexibility of the use of the liquid crystal writing tablet.

[0057] Among LCD handwriting tablets capable of partial erasure, some achieve this through a combination of voltage control by a driving circuit and a positioning device. This method typically results in imprecise erasure boundaries, is prone to accidental erasures, and consumes more power, undoubtedly increasing equipment costs and reducing reliability. Other LCD handwriting tablets achieve partial erasure through illumination. This method reduces equipment costs, but during the erasure process, the handwriting information in non-illuminated areas gradually fades over time, severely impacting the user experience.

[0058] In the liquid crystal handwriting tablet of this disclosure embodiment, the photosensitive device can only be turned on by the joint control of control voltage, pixel voltage and light illumination, thereby realizing the purpose of erasing a certain position with the help of light illumination, while the non-illuminated area is unaffected. In addition, the liquid crystal handwriting tablet of this disclosure embodiment does not require a positioning device, which simplifies the driving circuit and reduces the equipment cost.

[0059] Figure 2 This is a schematic diagram of the film layer structure of a liquid crystal panel in a liquid crystal handwriting tablet provided in this embodiment of the present disclosure. Figure 2As shown, the photosensitive device 102 can be a phototransistor, and each pixel electrode 101 can be electrically connected to at least one phototransistor. Thus, the driving component 002 can selectively apply pixel voltages to the pixel electrodes 102 in the liquid crystal panel 001 through multiple phototransistors, thereby applying pixel voltages to pixel electrodes 102 in a partial area of ​​the liquid crystal panel 001, and thus enabling localized erasure of the liquid crystal writing tablet 000 in erase mode. The liquid crystal writing tablet of this embodiment does not require the cooperation of a positioning device. When the liquid crystal writing tablet 000 is in erase mode, pixel voltages can be applied to all pixel electrodes 101 in the liquid crystal panel 001. Since the pixel voltage applied to each pixel electrode 102 is typically small, the power consumption of the liquid crystal writing tablet 000 is effectively reduced, and the service life of the liquid crystal writing tablet 000 is effectively improved.

[0060] In some exemplary embodiments, the phototransistor can be an N-type thin-film transistor or a P-type thin-film transistor. The following description uses an N-type thin-film transistor as an example.

[0061] In some exemplary embodiments, Figure 3 yes Figure 2 The image shows a top view of the liquid crystal panel in the phototransistor region of the liquid crystal writing tablet. Figure 4 yes Figure 2 A top view of a phototransistor is shown. Figure 2 , Figure 3 and Figure 4 As shown, the phototransistor may include a first electrode 102a and a second electrode 102b. The first electrode 102a may be one of a source and a drain, and the second electrode 102b may be the other of a source and a drain. The first electrode 102a includes a U-shaped structure, and the second electrode 102b includes a strip-shaped structure. One end of the second electrode 102b is located within the U-shaped structure of the first electrode 102a, and the other end is electrically connected to the pixel electrode 101.

[0062] In some exemplary implementations, such as Figure 3 As shown, the first electrode 102a has a first extension A, a second extension B, and a third extension C connected in sequence. The first extension A and the third extension C of the first electrode 102a extend in the same direction, and the second extension B of the first electrode 102a is perpendicular to the extension direction of the first extension A and the extension direction of the third extension C. Thus, the sequentially connected first extension A, second extension B, and third extension C form a U-shaped structure in the first electrode 102a.

[0063] The second electrode 102b has: a first connecting portion D located between the first extension portion A and the third extension portion C of the first electrode 102a, and a second connecting portion E connected to the first connecting portion D, wherein the first connecting portion D of the second electrode 102b is a strip structure in the second electrode 102b, and the second connecting portion E of the second electrode 102b is a block structure and is electrically connected to the pixel electrode 101.

[0064] In some exemplary implementations, such as Figure 2 and Figure 4 As shown, the phototransistor may further include a semiconductor layer pattern 102c that overlaps with the first electrode 102a and the second electrode 102b. The semiconductor layer pattern 102c includes an active layer 102c1 and an ohmic contact layer 102c2 disposed on the active layer 102c1. The active layer 102c1 is electrically connected to the first electrode 102a and the second electrode 102b through the ohmic contact layer 102c2.

[0065] In some exemplary embodiments, the active layer 102c1 is made of amorphous silicon (a-Si) with a thickness of 1500 to 2100 angstroms. In this embodiment, the active layer 102c1 is the main photosensitive portion. When light shines on the active layer 102c1, the leakage current increases due to the formation of photogenerated carriers, resulting in different conductivities of the TFT before and after illumination. To obtain better photosensitivity, the active layer 102c1 is made of a-Si, which has better photosensitivity than monocrystalline silicon, and the thickness of the a-Si is designed to be... .

[0066] In some exemplary embodiments, the ohmic contact layer 102c2 is made of N-type doped amorphous silicon (n... + a-Si), its function is to improve conductivity.

[0067] In some exemplary implementations, such as Figure 3 As shown, when the first electrode 102a in the phototransistor includes a U-shaped structure and the second electrode 102b includes a strip-shaped structure extending one end into the U-shaped structure, the channel region F of the active layer 102c1 is a U-shaped channel region. It should be noted that the channel region F of the active layer 102c1 refers to the region within the active layer 102c1 located between the region where the active layer 102c1 contacts the first electrode 102a and the region where the active layer 102c1 contacts the second electrode 102b.

[0068] A key parameter affecting the on-state current (Ion) and off-state current (Ioff) of a phototransistor is the aspect ratio (W / L) of the channel region in its active layer 102c1. Generally, as the aspect ratio (W / L) increases, the ratio of on-state current to off-state current (Ion / Ioff) also increases accordingly. When the channel region F of the active layer 102c1 in this phototransistor is a U-shaped channel region, due to the large aspect ratio of this U-shaped channel region, the phototransistor can obtain a higher on-state current value and withstand a higher breakdown voltage. This allows for more flexible voltage regulation and can also improve the lifespan of the LCD handwriting tablet.

[0069] In some exemplary embodiments, the channel region F of the active layer 102c1 has two first strip regions extending in the same direction and of the same length, and a second strip region for connecting the two first strip regions. The widths of the first strip region and the second strip region are the same. In this disclosure, the length of the channel region F of the active layer 102c1 is the sum of the lengths of the two first strip regions, and the width of the channel region F is the width of either the first strip region or the second strip region.

[0070] In some exemplary embodiments, the length of the channel region F of the active layer 102c1 can be from 45 micrometers to 55 micrometers, and the width can be from 4 micrometers to 6 micrometers, for example, Figure 4 As shown, the length of the channel region F of the active layer 102c1 can be 24.3 micrometers * 2 = 48.6 micrometers, and the width can be 5.16 micrometers. In this way, the phototransistor can meet the current required for pixel driving while being able to withstand a high breakdown voltage.

[0071] Figure 5 This is a schematic diagram illustrating the photosensitive test results of a phototransistor as a function of drain voltage Vd, as an exemplary embodiment of this disclosure. Figure 5 As shown, under the condition of gate voltage Vg = 0V, the current value increases sharply and significantly before and after illumination. When the drain voltage Vd = 20V, the ratio of the output current after illumination to that before illumination can reach 10. 4 However, the increase in output current with drain voltage Vd is limited.

[0072] Figure 6 This is a schematic diagram illustrating the photosensitive transistor's photosensitive test results as the brightness of the light source changes, as an exemplary embodiment of this disclosure. Figure 6 As shown, under the conditions of Vg = 0V and Vd = 20V, increasing the output brightness of the light source will continuously increase the output current Id, but it is still difficult to exceed 10V. -6 A. The above results indicate that increasing Vd and illumination intensity can increase the output current, but the increase is relatively limited.

[0073] Figure 7This is a schematic diagram illustrating the photosensitive transistor's photosensitive test results as a function of the gate voltage Vg, as an exemplary embodiment of this disclosure. Figure 7 As shown, the magnitude of the gate voltage Vg also affects the output current. When Vg is between a and b, the output current value is around 10. -13 Up to 10 -6 Within the range of A, the output current increases most rapidly with the gate voltage Vg. Where a≈-5V, b≈5V.

[0074] By utilizing the above characteristics of phototransistors, and by controlling the gate voltage, drain voltage, and illumination intensity, it is possible to turn on the phototransistor when a certain brightness of light is applied, and turn off the phototransistor in the absence of light or in a low light environment.

[0075] Considering that excessively bright light sources can damage human vision, while insufficient brightness may result in incomplete erasure, the brightness needs to be controlled within a suitable range. This range satisfies the requirements of light-based erasure while avoiding damage to the eyes. Correspondingly, the gate voltage Vg and drain voltage Vd must also be controlled within a suitable range so that erasure only occurs when the light intensity exceeds a certain value, while non-illuminated areas remain unaffected. The gate voltage Vg can be... Figure 7 Choose the voltage range corresponding to the interval where the medium current increases the fastest, such as... Figure 7 The range from a to b shown can be used to obtain both a suitable off-state current and an on-state current that does not fully turn on the phototransistor. The drain voltage Vd can be adjusted as needed.

[0076] In one exemplary embodiment, the gate voltage Vg is adjusted so that the output current of the phototransistor under no-light conditions is 10. -13 ~10 -10 A (as) Figure 7 As shown, Vg can range from -5V to -2V, and the drain voltage Vd can be adjusted from 10V to 60V as needed. In this state, the phototransistor can be considered to be off. Figure 8 As shown, the LCD handwriting tablet can operate simultaneously in erase and writing modes. In this mode, the driving component provides a third range of control voltage to the control electrodes of multiple photosensitive devices and a fourth range of pixel voltage to the first electrodes of the multiple photosensitive devices. The third range of control voltage is between -5V and -2V, and the second range of pixel voltage is between 10V and 60V. At this time, the gate voltage Vg and drain voltage Vd are always in the voltage-on state, and the phototransistors can be turned on only when a certain level of illumination (such as 20,000 nits to 40,000 nits) is provided. This mode is suitable for scenes with high ambient brightness and is easy to operate, but it may consume more power.

[0077] In another exemplary embodiment, the gate voltage Vg is adjusted so that the output current of the phototransistor under no-light conditions is 10. -10 ~10 -7 A (as) Figure 7 As shown, Vg can range from -2V to 5V, and the drain voltage Vd can be adjusted from 20V to 40V as needed. In this state, the phototransistor can be considered to be in a semi-open state. Figure 9 As shown, the LCD writing tablet can switch between erase and writing modes via a toggle switch. In writing mode, the driving component does not provide control voltage or pixel voltage to the photosensitive devices. Writing can be done on the LCD writing tablet using a writing tool (e.g., a stylus). Some liquid crystal molecules in the liquid crystal layer are subjected to external pressure, causing them to invert and reflect visible light, thus displaying the written handwriting. In erase mode, the driving component provides a first range of control voltage to the control electrodes of multiple photosensitive devices and a second range of pixel voltage to the first electrodes of the multiple photosensitive devices. The first range of control voltage is between -2V and 5V, and the second range of pixel voltage is between 20V and 40V. In erase mode, a certain amount of light (e.g., 5000 nits to 20000 nits) is sufficient for quick erasure. This mode is suitable for environments with normal or low brightness and is more energy-efficient than the previous mode.

[0078] exist Figure 8 and Figure 9 In the timing diagram shown, a certain low voltage is applied to the drain voltage Vd after the phototransistor finishes operating. This is to allow the voltage stored in the pixel to be fully released for better erasure in the next operation. For example, for... Figure 7 The phototransistor designed shown outputs a current value Id ≈ 10 when the gate voltage Vg = 0V. -9 A. Adjust Vd = 20V. When the brightness of the light source exceeds 10,000 nits, a better erasing effect can be obtained.

[0079] In some exemplary embodiments, please refer to Figure 2 , Figure 3 and Figure 4The first substrate 100 may further include a first substrate 103, with the phototransistor and pixel electrode 101 both located on the first substrate 103. The phototransistor may further include a gate 102d and a gate insulating layer 102e. The gate 102d is located on the side of the semiconductor layer pattern 102c closest to the first substrate 103, the gate insulating layer 102e is located between the gate 102d and the semiconductor layer pattern 102c, and the first electrode 102a and the second electrode 102b are both located on the side of the semiconductor layer pattern 102c furthest from the first substrate 103, and both the first electrode 102a and the second electrode 102b overlap with the semiconductor layer pattern 102c. That is, the phototransistor can be a bottom-gate type phototransistor. In other possible implementations, the phototransistor can also be a top-gate type phototransistor, which is not limited in this embodiment.

[0080] In some exemplary embodiments, the first substrate 103 may be a glass substrate.

[0081] In some exemplary embodiments, Figure 10 yes Figure 2 The top view of the LCD panel in the LCD handwriting tablet is shown, as follows: Figure 2 and Figure 10 As shown, the first substrate 100 may further include data lines 104 and gate lines 105 located on the first substrate 103 and intersecting in their extending directions. The intersecting data lines 104 and gate lines 105 can define a plurality of pixel regions 001a in the liquid crystal panel 001. For example, any two adjacent data lines 104 and any two adjacent gate lines 105 can form a pixel region 001a. Each pixel electrode 101 on the first substrate 100 can be located within a pixel region 001a.

[0082] In some exemplary embodiments, the pixel region 001a can be a rectangular area with a length and width of 1 mm. This reduces user dizziness when viewing the LCD panel while ensuring the LCD panel 001 has a high resolution. When the resolution of the LCD panel 101 is high, the area of ​​the minimum erasable area (i.e., one pixel area) of the LCD handwriting tablet 000 is small, effectively improving the erasing accuracy of the LCD handwriting tablet 000.

[0083] In some exemplary embodiments, data line 104 is electrically connected to the first electrode 102a in the phototransistor, and gate line 105 is electrically connected to the gate 102d in the phototransistor. For example, data line 104 is disposed on the same layer as the first electrode 102a and the second electrode 102b; that is, data line 104, the first electrode 102a, and the second electrode 102b are formed in a single patterning process. Gate line 105 is disposed on the same layer as the gate 102d; that is, gate line 105 and gate 102d are formed in a single patterning process.

[0084] In some exemplary embodiments, the thickness of the data line 104 and the first electrode 102a, and the gate line 105 and the gate 102d, can range from 350 to 450 nanometers. For example, the thickness of the data line 104 and the first electrode 102a, and the gate line 105 and the gate 102d, can all be 400 nanometers. The materials of the data line 104 and the gate line 105 can both include metallic materials such as aluminum, molybdenum, or alloys. This can reduce the resistance of the data line 104 and the gate line 105.

[0085] In some exemplary embodiments, both the data line 104 and the gate line 105 are also electrically connected to the driving component 002. The driving component 002 may include a timing controller (TCON), a source driver, and a gate driver. For example, the timing controller is electrically connected to both the source driver and the gate driver, the data line 104 in the liquid crystal panel 001 is electrically connected to the source driver, and the gate line 105 in the liquid crystal panel 001 is electrically connected to the gate driver.

[0086] The timing controller's main function is to generate corresponding data and control signals. The data signals are transmitted to the source driver, which converts the received data signals into pixel voltages and writes them to the corresponding pixel areas on the liquid crystal panel 001 via data line 104. The control signals are transmitted to the gate driver, which converts the received control signals into gate voltages and writes them to the corresponding pixel areas on the liquid crystal panel 001 via gate line 105, thereby achieving independent control of individual pixel electrodes on the liquid crystal panel 001.

[0087] In some exemplary embodiments, the width of the data line 104 and the gate line 105 can range from 8 to 12 micrometers. For example, the width of both the data line 104 and the gate line 105 can be 10 micrometers. This can further reduce the resistance of the data line 104 and the gate line 105, and at the same time, reduce the probability of visible grid lines appearing on the liquid crystal panel 001 due to reflections from the data line 104 and the gate line 105, thereby improving the display effect of the liquid crystal handwriting tablet 000.

[0088] In some exemplary embodiments, the spacing between the plurality of block-shaped pixel electrodes 101 can range from 18 micrometers to 22 micrometers, for example, the spacing between the plurality of block-shaped pixel electrodes 101 can be 20 micrometers. In this way, the spacing between the pixel electrodes 101 and the data lines 104 and the gate lines 105 is large, which can reduce the parasitic capacitance between the pixel electrodes 101 and the data lines 104 and the gate lines 105.

[0089] In some exemplary embodiments, Figure 11 This is a schematic diagram of the film layer structure of the liquid crystal panel in another liquid crystal handwriting tablet provided in this disclosure embodiment. Figure 12 yes Figure 11 Please refer to the top view of the LCD panel in the LCD handwriting tablet shown. Figure 11 and Figure 12 The first substrate 100 may further include an auxiliary electrode line 106 located on the first substrate 103 and disposed in the same layer as the gate line 105. The auxiliary electrode line 106 extends in the same direction as the gate line 105.

[0090] In some exemplary embodiments, the pixel electrodes 101 in the first substrate 100 are arranged in multiple rows, and the number of auxiliary electrode lines 106 in the first substrate 100 is the same as the number of rows of pixel electrodes 101. The orthographic projection of each auxiliary electrode line 106 on the first substrate 103 overlaps with the orthographic projection of the corresponding row of pixel electrodes 101 on the first substrate 103. The auxiliary electrode line 106 can form a storage capacitor with each pixel electrode 101 in a row of pixel electrodes 101. This storage capacitor can be used to maintain the charging voltage of the pixel electrode 101. When the liquid crystal handwriting tablet 000 is in the erase mode, this storage capacitor can prevent voltage changes in the pixel area 001a at the erase location from affecting the voltage of the surrounding pixel areas 001a, thereby avoiding affecting the display effect of the surrounding pixel areas 001a.

[0091] In some exemplary implementations, please refer to Figure 2 and Figure 11 The first substrate 100 may further include: a passivation layer 107 located on the phototransistor and a first planarization layer 108 located on the passivation layer 107. A pixel electrode 101 is located on and in contact with the first planarization layer 108. The passivation layer 107 and the first planarization layer 108 have through-holes a, and the pixel electrode 101 is electrically connected to a second electrode 102b through the through-holes a. The passivation layer 107 and the first planarization layer 108 can be used to protect the phototransistor.

[0092] In some exemplary embodiments, Figure 13 This is a schematic diagram of the film layer structure of the liquid crystal panel in another embodiment of the liquid crystal handwriting tablet provided in this disclosure. Please refer to it. Figure 13 The first substrate 100 may further include a second planarization layer 109 located on the pixel electrode 101. When the first substrate 100 and the second substrate 200 are arranged opposite each other, foreign objects may appear between the first substrate 100 and the second substrate 200 due to the non-clean environment of the device. The second planarization layer 109 can be used to prevent foreign objects located between the first substrate 100 and the second substrate 200 and to conduct electricity between the pixel electrode 101 in the first substrate 100 and the common electrode 201 in the second substrate 200.

[0093] In some exemplary embodiments, please refer to Figure 2 , Figure 11 and Figure 13 The liquid crystal panel 001 also includes a spacer 400 located between the first substrate 100 and the second substrate 200. The spacer 400 isolates the first substrate 100 and the second substrate 200. Simultaneously, the spacer 400 has a certain elasticity, allowing the liquid crystal writing tablet 000 to undergo elastic deformation under external pressure. Furthermore, the spacer 400 supports the liquid crystal layer 300, preventing the arrangement of liquid crystal molecules in the liquid crystal layer 300 from being affected when the liquid crystal panel 001 is pressed, thus improving the display effect of the liquid crystal writing tablet 000.

[0094] In some exemplary embodiments, the liquid crystal layer 300 includes bistable liquid crystal molecules. These bistable liquid crystal molecules have a planar texture (P-state), a focal conic texture (FC-state), and a hometropic texture (H-state). The P-state and FC-state are stable states that can be maintained without voltage, while the H-state is an unstable state that is presented when a voltage is continuously applied. When the liquid crystal writing tablet 000 is subjected to external pressure, the bistable liquid crystal molecules in the liquid crystal layer 300 flip to the P-state under the external pressure, reflecting visible light. The area of ​​the liquid crystal panel 001 subjected to external pressure displays the written handwriting. When the driving component 002 in the liquid crystal writing tablet 000 applies a pixel voltage to the pixel electrode 101 in the area to be erased, a voltage difference is formed between the pixel electrode 101 and the common electrode 201 in the area to be erased. Under the action of this voltage difference, the bistable liquid crystal molecules in the area to be erased rearrange to the FC-state, no longer reflecting visible light. In this case, the written handwriting in the area to be erased can be erased.

[0095] In some exemplary implementations, such as Figure 2 , Figure 11 and Figure 13 As shown, the second substrate 200 may further include a second substrate 202. The second substrate 202 may be a flexible substrate, and the material of the second substrate 202 may include polyethylene terephthalate (PET). The common electrode 201 is located on the second substrate 202.

[0096] In summary, the liquid crystal writing tablet provided in this embodiment includes a liquid crystal panel and a driving assembly. The liquid crystal panel includes a first substrate and a second substrate disposed opposite to each other, and a liquid crystal layer located between the first substrate and the second substrate. The first substrate includes multiple pixel electrodes and multiple photosensitive devices electrically connected to the multiple pixel electrodes. These photosensitive devices can only be activated under the combined control of a control voltage of a certain intensity, a pixel voltage, and illumination. When the liquid crystal writing tablet is in erase mode, the driving assembly electrically connected to the liquid crystal panel provides a control voltage to the control electrode of the multiple photosensitive devices and a pixel voltage to the first electrode of the multiple photosensitive devices. Then, an erasing tool emits light of a first intensity to the area to be erased, activating the photosensitive devices in the area to be erased. This creates a voltage difference between the pixel electrode and the common electrode in the area to be erased, causing the liquid crystal molecules in the liquid crystal layer located in the area to be erased to rearrange under the action of this voltage difference. Thus, localized erasure of the liquid crystal writing tablet is achieved through illumination, while non-illuminated areas remain unaffected. Furthermore, the liquid crystal writing tablet of this embodiment does not require a positioning device, simplifying the driving circuit and reducing equipment costs.

[0097] This disclosure also provides a method for manufacturing a liquid crystal panel. This method is used to form the liquid crystal panel described in the above embodiments. The method may include:

[0098] Step A1: Form a gate pattern, a gate insulating layer, a semiconductor layer pattern, a source / drain pattern, a first planarization layer, a pixel electrode, and a second planarization layer on a first substrate to obtain a first substrate.

[0099] For example, firstly, a gate layer is formed on a first substrate, and a patterning process is performed on the gate layer to form a gate pattern. The gate pattern may include a gate, and gate lines and auxiliary electrode lines connected to the gate. For example, the first substrate may be a glass substrate. The material of the gate pattern may include metallic materials such as aluminum, molybdenum, or alloys. The gate lines are used to apply a gate voltage to the gate.

[0100] Next, a gate insulating layer is formed on a first substrate on which the gate pattern is formed. This gate insulating layer is used to protect the gate lines. Exemplarily, the material of the gate insulating layer may include silicon dioxide, silicon nitride, or a mixture of silicon dioxide and silicon nitride.

[0101] Subsequently, an active material thin film is formed on a first substrate on which a gate insulating layer is formed, and a patterning process is performed on the active material thin film to form an active layer pattern. For example, the material of the active layer pattern can be amorphous silicon. Since amorphous silicon has better photosensitivity than monocrystalline silicon, the active layer material in this embodiment of the disclosure is selected as amorphous silicon. The thickness of the active layer pattern can be from 1500 to 2100 angstroms.

[0102] Subsequently, the source and drain regions of the active layer are heavily doped using an ion implantation process to form an ohmic contact layer.

[0103] Subsequently, a source / drain electrode layer is formed on a first substrate having an ohmic contact layer pattern, and a patterning process is performed on the source / drain electrode layer to form a source / drain pattern. This source / drain pattern may include a first electrode, a second electrode, and a data line. The first electrode may be one of the source and drain electrodes, and the second electrode may be the other of the source and drain electrodes. For example, the material of the source / drain pattern may include aluminum.

[0104] Subsequently, a passivation layer and a first planarization layer are sequentially formed on the first substrate on which the active drain pattern is formed. The passivation layer and the first planarization layer have vias through which the subsequently formed pixel electrode can be electrically connected to the second electrode in the source-drain pattern. For example, the passivation layer can be made of any one or more of silicon oxide (SiOx), silicon nitride (SiNx), and silicon oxynitride (SiON), and can be a single layer, multiple layers, or a composite layer. The material of the first planarization layer can include silicon dioxide, silicon nitride, or a mixture of silicon dioxide and silicon nitride.

[0105] Subsequently, a first conductive thin film is formed on a first substrate on which a first planarization layer is formed, and a patterning process is performed on the conductive thin film to form a plurality of block-shaped pixel electrodes. For example, the material of the plurality of block-shaped pixel electrodes may include transparent conductive materials such as indium tin oxide (ITO) or indium zinc oxide (IZO).

[0106] Finally, a second planar thin film is formed on the first substrate on which the pixel electrode is formed, and a patterning process is performed on the second planar thin film to form a second planarization layer.

[0107] The first substrate can be formed through the above process. A single patterning process in the above embodiments may include: photoresist coating, exposure, development, etching, and photoresist stripping.

[0108] Step A2: Form spacers and a sealing frame on the first substrate.

[0109] For example, firstly, an organic film is formed on a second planarization layer in a first substrate, and a patterning process is performed on the organic film to form a spacer.

[0110] Subsequently, a sealing frame material is applied to the periphery of the first substrate with spacers to form a sealing frame.

[0111] Step A3: Form a common electrode on the second substrate to obtain the second substrate.

[0112] For example, a second conductive thin film is formed on a second substrate, and a patterning process is performed on the second conductive thin film to form a common electrode.

[0113] The second substrate is a flexible substrate, and the material of the second substrate may include PET. The common electrode is a planar electrode, and the material of the common electrode may include ITO or IZO.

[0114] The second substrate can be formed through the above process.

[0115] Step A4: Inject liquid crystal molecules into the sealing frame to form a liquid crystal layer. For example, the liquid crystal molecules may include bistable liquid crystal molecules.

[0116] Step A5: Cover the liquid crystal layer with a second substrate, such that the common electrode in the second substrate faces the first substrate, and the pixel electrode in the first substrate faces the second substrate.

[0117] The above steps A1 to A5 can be used to form Figure 13 The LCD panel shown.

[0118] This disclosure also provides a handwriting device; please refer to... Figure 14 , Figure 14 This is a schematic diagram of a handwriting device provided in an embodiment of this disclosure. The handwriting device can be any product or component with a display function, such as a mobile phone, tablet computer, television, monitor, laptop computer, digital photo frame, or navigator; this disclosure is not limited to these. The handwriting device includes the aforementioned liquid crystal handwriting tablet 000, and also includes an erasing tool. The erasing tool includes an emitting light source and a control switch, the control switch being used to control the emitting light source to turn on or off.

[0119] In some exemplary embodiments, the light emitted by the light source may include any one of the following: infrared light, ultraviolet light, and visible light, etc.

[0120] In this disclosure, there are multiple ways to switch between erasing mode and writing mode on the LCD handwriting tablet 000. The embodiments of this disclosure illustrate the following two possible implementation methods as examples.

[0121] In some exemplary implementations, such as Figure 15 As shown, the handwriting device may further include a switch 010. The switch 010 is electrically connected to the driving assembly. The switch 010 is configured to control the LCD handwriting pad 000 to switch between erase mode and writing mode.

[0122] When the switch 010 is turned on, the LCD handwriting pad 000 switches to erase mode. In this mode, the driving component provides a first range of control voltage to the control electrodes of multiple photosensitive devices and a second range of pixel voltage to the first electrodes of the multiple photosensitive devices. At this time, the photosensitive devices can be considered to be in a semi-open state. Assuming that the user uses an erasing tool to perform an erasing operation on the LCD handwriting pad 000, the erasing tool emits light with a first intensity of illumination to the area to be erased. As a result, the photosensitive devices in the area to be erased turn on, and a voltage difference is formed between the pixel electrode and the common electrode in the area to be erased. This causes the liquid crystal molecules in the liquid crystal layer located in the area to be erased to rearrange under the action of the voltage difference, and the writing in the area to be erased in the liquid crystal panel is erased.

[0123] When the switch 010 is turned off, the LCD handwriting tablet 000 switches to writing mode. In this mode, the driving component does not provide control voltage or pixel voltage to the photosensitive device. At this time, writing can be done on the LCD handwriting tablet 000 using a writing tool (e.g., a writing pen). Some liquid crystal molecules in the liquid crystal layer 300 are subjected to external pressure, causing the liquid crystal molecules to invert and reflect visible light. The LCD handwriting tablet 000 then displays the written handwriting.

[0124] In some exemplary embodiments, the writing instrument and the erasing instrument may also be a single integrated structure.

[0125] In other exemplary embodiments, such as Figure 14 As shown, the LCD handwriting tablet 000 does not have a switch 010. The LCD handwriting tablet 000 operates simultaneously in writing mode and erase mode. Users can write on the LCD handwriting tablet 000 using a writing tool (e.g., a stylus). Under external pressure, some liquid crystal molecules in the liquid crystal layer reverse their direction, reflecting visible light, and the LCD handwriting tablet 000 displays the written handwriting. Users can also erase on the LCD handwriting tablet 000 using an eraser tool. During erasure, the eraser tool emits light of a certain intensity. In this mode, the driving component provides a third range of control voltage to the control electrodes of multiple photosensitive devices and a fourth range of pixel voltage to the first electrodes of multiple photosensitive devices. At this time, the photosensitive devices can be considered to be in an off state. Assuming the user uses an eraser tool to erase on the LCD handwriting tablet 000, the eraser tool emits light of a first intensity to the area to be erased. In this way, the photosensitive device in the area to be erased is turned on, and a voltage difference is formed between the pixel electrode and the common electrode in the area to be erased. This causes the liquid crystal molecules in the liquid crystal layer located in the area to be erased to rearrange under the action of the voltage difference, and the writing marks in the area to be erased in the liquid crystal panel are erased.

[0126] At the end of each erasure operation (i.e., when the light emission to the area to be erased stops), the driving component provides a low voltage to the first electrode of multiple photosensitive devices for a certain duration, so that the voltage stored in the pixel electrode can be fully released for better erasure next time.

[0127] In summary, the handwriting device provided in this disclosure, by incorporating a photosensitive device that can only be activated under the combined control of a certain intensity of control voltage, pixel voltage, and illumination, enables the erasure of localized areas of the liquid crystal handwriting tablet through illumination, while un-illuminated areas remain unaffected. Furthermore, the handwriting device of this disclosure does not require a positioning device, simplifying the driving circuitry and reducing equipment costs.

[0128] This disclosure also provides a control method for a liquid crystal writing tablet, which can be applied to the liquid crystal writing tablet described in the above embodiments. The control method for the liquid crystal writing tablet may include:

[0129] Step 100: When the liquid crystal handwriting tablet is in erase mode, the driving component provides a control voltage to the control electrode of the plurality of photosensitive devices and a pixel voltage to the first electrode of the plurality of photosensitive devices.

[0130] In this embodiment of the disclosure, the LCD handwriting tablet can be controlled to be in the erasure state by switching on a switch.

[0131] Step 101: The area to be erased receives light with an illumination intensity of the first level, and the photosensitive device in the area to be erased is turned on.

[0132] Step 102: A voltage difference is formed between the pixel electrode and the common electrode in the area to be erased, and the liquid crystal molecules in the area to be erased rearrange under the action of the voltage difference.

[0133] While the embodiments disclosed herein are as described above, the content is merely for the purpose of facilitating understanding of this disclosure and is not intended to limit this disclosure. Any person skilled in the art may make any modifications and changes to the form and details of the implementation without departing from the spirit and scope of this disclosure; however, the scope of patent protection of this disclosure shall still be determined by the scope defined in the appended claims.

Claims

1. A liquid crystal handwriting pad, characterized by, The liquid crystal panel and a driving assembly electrically connected with the liquid crystal panel, wherein: The liquid crystal panel comprises a first substrate and a second substrate arranged oppositely, and a liquid crystal layer between the first substrate and the second substrate, the first substrate comprises a plurality of pixel electrodes and a plurality of photosensitive devices electrically connected with the plurality of pixel electrodes; the second substrate comprises a planar common electrode; The driving assembly is configured to provide a control voltage to the control electrode of the plurality of photosensitive devices, and provide a pixel voltage to the first electrode of the plurality of photosensitive devices, so that the photosensitive devices in the to-be-erased area are turned on, the to-be-erased area is an area receiving light with a first intensity of light intensity, and a voltage difference is formed between the pixel electrode and the common electrode in the to-be-erased area; The photosensitive device is a photosensitive transistor, and the photosensitive transistor is turned on under the joint control of the control voltage, the pixel voltage and the light with the first intensity. When the control voltage is -5V to -2V and the pixel voltage is 10V to 60V, the output current of the photosensitive transistor under no light condition is 10 -13 ~10 -10 A, the photosensitive transistor is in the off state, and the liquid crystal handwriting board can work in the erasing mode and the writing mode simultaneously; when the first intensity is 20000 to 40000 nits, the photosensitive transistor is turned on. When the control voltage is -2V to 5V and the pixel voltage is 20V to 40V, the output current of the photosensitive transistor under no light condition is 10 -10 ~10 -7 A, the photosensitive transistor is in a semi-open state, and the liquid crystal handwriting board can switch between an erasing mode and a writing mode; in the erasing mode, when the first intensity of the light illumination is 5000 to 20000 nits, the erasing of the to-be-erased area can be realized.

2. The liquid crystal handwriting pad of claim 1, wherein, The first substrate further comprises a plurality of scan signal lines and a plurality of data signal lines, the plurality of scan signal lines extend in a first direction, and the plurality of data signal lines extend in a second direction, the first direction and the second direction intersect. The gate electrode of the photosensitive transistor is connected with the scan signal line, the first electrode of the photosensitive transistor is electrically connected with the data signal line, and the second electrode of the photosensitive transistor is electrically connected with the pixel electrode.

3. The liquid crystal handwriting pad of claim 2, wherein, The first electrode of the photosensitive transistor comprises a U-shaped structure, the second electrode of the photosensitive transistor comprises a strip-shaped structure, one end of the second electrode is located in the U-shaped structure, and the other end of the second electrode is electrically connected with the pixel electrode.

4. The liquid crystal handwriting pad of claim 2, wherein, The first substrate comprises a first substrate, a gate layer arranged on the first substrate, a gate insulating layer arranged on the gate layer, a semiconductor layer arranged on the gate insulating layer, a source-drain electrode layer arranged on the semiconductor layer, a passivation layer arranged on the source-drain electrode layer, and a first planar layer arranged on the passivation layer; The scan signal line, the gate electrode of the photosensitive transistor and the gate layer are arranged in the same layer. The data signal line, the first electrode and the second electrode of the photosensitive transistor are arranged in the same layer as the source-drain electrode layer.

5. The liquid crystal handwriting pad of claim 4, wherein, The semiconductor layer comprises an active layer and an ohmic contact layer arranged on the active layer, and the active layer is electrically connected with the first electrode and the second electrode through the ohmic contact layer.

6. The liquid crystal handwriting pad of claim 5, wherein, The active layer comprises a channel region, the width of the channel region is 45-55 microns, and the length of the channel region is 4-6 microns.

7. The liquid crystal handwriting pad of claim 5, wherein, The material of the active layer is amorphous silicon, and the thickness is 1500-2100 angstroms.

8. A handwriting device, characterized by The liquid crystal handwriting board according to any one of claims 1-7 further comprises an erasing tool, the erasing tool comprises an emitting light source and a control switch, and the control switch is used to control the opening or closing of the emitting light source. Further comprising a switching switch electrically connected with the driving assembly, wherein:

9. The handwriting device according to claim 8, wherein When the switching switch is turned on, the driving assembly provides a control voltage in a first range to the control electrode of the plurality of photosensitive devices, and provides a pixel voltage in a second range to the first electrode of the plurality of photosensitive devices. ​ 10. A control method of a liquid crystal handwriting tablet, characterized by, The liquid crystal handwriting board comprises a liquid crystal panel and a driving assembly electrically connected with the liquid crystal panel; the liquid crystal panel comprises a first substrate and a second substrate arranged oppositely, and a liquid crystal layer between the first substrate and the second substrate; the first substrate comprises a plurality of pixel electrodes and a plurality of photosensitive devices electrically connected with the plurality of pixel electrodes; the second substrate comprises a planar common electrode; the control method comprises: The driving assembly provides a control voltage to the control electrode of the plurality of photosensitive devices, and provides a pixel voltage to the first electrode of the plurality of photosensitive devices; The to-be-erased area receives light rays with a first intensity of light illumination, and the photosensitive devices in the to-be-erased area are turned on; A voltage difference is formed between the pixel electrode and the common electrode in the to-be-erased area, and the liquid crystal molecules in the to-be-erased area are rearranged under the action of the voltage difference; The photosensitive device is a photosensitive transistor, and the photosensitive transistor is turned on under the joint control of the control voltage, the pixel voltage and the light rays with the first intensity. When the control voltage is -5V to -2V and the pixel voltage is 10V to 60V, the output current of the photosensitive transistor under no light condition is 10 -13 ~10 -10 A, the photosensitive transistor is in the off state, and the liquid crystal handwriting board can work in the erasing mode and the writing mode simultaneously; when the first intensity is 20000 to 40000 nits, the photosensitive transistor is turned on. When the control voltage is -2V to 5V and the pixel voltage is 20V to 40V, the output current of the photosensitive transistor under no light condition is 10 -10 ~10 -7 A, the photosensitive transistor is in a semi-open state, and the liquid crystal handwriting board can switch between an erasing mode and a writing mode; in the erasing mode, when the first intensity of the light illumination is 5000 to 20000 nits, the erasing of the to-be-erased area can be realized.

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