CN118192132A - Bistable display element and reflective display device comprising same - Google Patents

Abstract

The invention provides a bistable display element and a reflective display device comprising the same, wherein the bistable display element comprises a first substrate and a second substrate which are oppositely arranged, and an electrochromic layer arranged between the first substrate and the second substrate, and the first substrate comprises a common electrode and a metal layer. According to the invention, the metal layer is arranged on the public electrode, so that the resistance of the public electrode is greatly reduced under the condition of not changing the reflectivity of the reflective display device, and the delay problem in the signal transmission process is improved, thereby meeting the requirement of alternating current driving.

Description

Bistable display element and reflective display device comprising same

Technical Field

The present disclosure relates to display technologies, and particularly to a bistable display element and a reflective display device including the bistable display element.

Background

With the development of display technology, flat panel display devices such as bistable Liquid crystal displays (Liquid CRYSTAL DISPLAY, LCD) have been widely used in various consumer electronic products such as mobile phones, televisions, personal digital assistants, digital cameras, notebook computers, and desktop computers, and have become the mainstream of display devices because of their advantages of high image quality, power saving, thin body, and wide application range.

Among the numerous bistable liquid crystal displays, electronic paper is becoming popular in the market with lower energy consumption and soft display effect like paper and use prospect that can replace paper. From the display mode, the electronic paper has display modes such as microcapsules, rotating balls, microcups, electrochemical reactions and the like, wherein the display modes of the microcapsules are more common. The basic display principle of the microcapsule is as follows: the electrophoresis liquid contains charged particles which can move under the action of an electric field and reflect ambient light to display images like paper so as to be received by human eyes; in the picture conversion stage, the position of charged particles in the electrophoretic fluid can be controlled according to the magnitude and time of the voltage applied to the two ends of the electrophoretic fluid, so that the intensity of emitted light is controlled to realize gray scale display; in the picture holding stage, the equipotential is applied to the two ends of the electrophoretic liquid, and the charged particles are kept in a certain state in the electrophoretic liquid, so that the static picture can be held with low energy consumption, and the static picture display can be realized.

In bistable liquid crystal display devices, an electric field perpendicular to the substrate surfaces is formed by electrode structures on the upper and lower substrate surfaces in a cell to control the movement of electrophoretic particles or the rotation of liquid crystals. Because of the different characteristics of the electrophoretic particles or the liquid crystal material, the required driving voltage is generally larger, usually larger than 20V, and even more than 30V in some special driving modes, the driving waveforms formed in the bistable display element are shown in fig. 1, the common electrode voltage is 0V, but the absolute value of the pixel electrode voltage is as high as 30V. However, it is difficult to support such high voltage by using a general driving chip, and a chip manufacturing process using a high-voltage process is required, which increases the cost of the driving chip and reduces the versatility of the chip. If the voltage of the alternating voltage on the pixel electrode is reduced to match the used chip, and the driving voltage between the upper substrate and the lower substrate is kept unchanged, the voltage of the upper substrate is also required to be an alternating voltage with a certain magnitude. However, there is a problem in that: because the common electrode of the upper substrate is a transparent glass electrode generally, the impedance is larger, larger signal transmission delay exists, and when the upper substrate is driven by alternating voltage, obvious signal delay exists at the near end and the far end, so that the display driving requirement cannot be met.

Disclosure of Invention

In order to eliminate the signal delay problem on the common electrode as much as possible under the premise of reducing the driving voltage required by the pixel electrode, the invention provides a bistable display element and a reflective display device comprising the bistable display element.

The bistable display element comprises a first substrate, a second substrate and an electrochromic layer, wherein the first substrate and the second substrate are oppositely arranged, the electrochromic layer is arranged between the first substrate and the second substrate, a common electrode and a metal layer are sequentially arranged on one side, close to the electrochromic layer, of the first substrate, and a pixel electrode is arranged on one side, close to the electrochromic layer, of the second substrate.

In some embodiments of the present invention, the first substrate is a transparent substrate, and the material of the first substrate may be a rigid substrate, for example: a glass plate or a polymethyl methacrylate (Polymethyl Methacrylate, PMMA) substrate, or may also be a flexible substrate, for example: a substrate made of Polyimide (PI) or polyethylene terephthalate (Polyethylene Terephthalate, PET) as a main component. In practical applications, the first substrate may be a rigid substrate or a flexible substrate made of other materials, besides the materials exemplified above, and the constituent materials thereof are not limited herein.

In some embodiments of the present invention, the second substrate may be the same as the first substrate, that is, the second substrate may also be a transparent substrate, and may be a rigid substrate or a flexible substrate as described above.

In some embodiments of the present invention, the second substrate may also be an opaque substrate, for example, a black opaque PMMA substrate, PI substrate, or PET substrate.

In some embodiments of the present invention, the first substrate is further provided with a black matrix, the black matrix may be in a net structure on the first substrate, and a plurality of empty areas arranged in an array are formed on the first substrate, and may also take other shapes suitable for application requirements, which is not limited in the present invention.

In some embodiments of the invention, the black matrix is disposed between the first substrate base plate and the common electrode.

In some embodiments of the present invention, the common electrode on the first substrate and the pixel electrode on the second substrate are made of the same material, and may be transparent conductive materials, which may be transparent conductive oxide (TRANSPARENT CONDUCTIVE OXIDE, TCO) or conductive polymer, for example: indium Tin Oxide (ITO), indium zinc Oxide (Indium Zinc Oxide, IZO), poly-3, 4-ethylenedioxythiophene (PEDOT), and the like.

In some embodiments of the invention, the metal layer is a mesh structure on the common electrode. Specifically, the metal layer is disposed on the common electrode, but is not necessarily in contact with the common electrode. Similarly, the pixel electrode is disposed on the second substrate, but is not necessarily in contact with the second substrate.

In some embodiments of the present invention, the area occupied by the metal layer on the common electrode coincides with the area occupied by the black matrix on the common electrode, and the area occupied by the metal layer does not exceed the area occupied by the black matrix. Specifically, the edge of the metal layer may overlap with the edge of the black matrix, or may be in a region where the black matrix is formed. In addition, "overlap" as used herein does not mean contact, but rather refers to a spatial relative positional relationship between regions.

In some embodiments of the present invention, the material of the metal layer may be common metals such as aluminum and copper, which are cheap and common, or may be other metals or alloys composed of several metals, which can achieve the technical effects of the present invention, and the material of the metal layer is not strictly limited herein.

In some embodiments of the invention, the resistance of the metal layer is not greater than the resistance of the common electrode. Since the metal layer is used as an electrode together with the common electrode to transmit a common signal, and the metal layer is used as a resistor for reducing the impedance of the common electrode, if the resistor is larger than the resistor of the common electrode, the problem of signal delay cannot be solved.

In some embodiments of the invention, the electrochromic layer is one of a charged particle layer or a liquid crystal molecular layer.

In some embodiments of the present invention, the electrochromic layer is a charged particle layer, and the microparticles contained therein may be selected from any one or more of microcapsules, microcups, rotating balls, and specifically, the microparticles may further contain charged color particles, for example, red particles, blue particles, green particles, white particles, black particles, and the like.

In some embodiments of the present invention, the electrochromic layer is a layer of liquid crystal molecules, wherein the liquid crystal molecules contained therein may be selected from any one or more combinations of nematic, smectic, and cholesteric liquid crystal molecules.

The invention also provides a preparation process of the bistable display element, which comprises the following steps:

S1: providing a first substrate, forming a black matrix on the first substrate, providing a second substrate, and forming a pixel electrode on the second substrate;

S2: forming a common electrode on the first substrate base plate; furthermore, the common electrode needs to be arranged on the surface of the black matrix, namely, the black matrix is arranged between the first substrate and the common electrode;

s3: forming a metal layer on the common electrode, wherein the metal layer and the common electrode are used as electrodes for signal transmission; further, the metal layer and the black matrix are preferably arranged in a superposed manner;

S4: and packaging charged particles or liquid crystal molecules in a closed space formed by the first substrate, the second substrate and the sealing glue through a filling process to form an electrochromic layer, thus obtaining the bistable display element.

In some embodiments of the present invention, the processing means used to form the metal layer on the common electrode in S3 may be one of plasma sputtering, exposure, and etching, and may be implemented by selecting other suitable processing technologies in the technical field according to the metal type used, which is not limited strictly herein.

In some embodiments of the present invention, the chemical composition of the encapsulant used to encapsulate the charged particles or liquid crystal molecules in S4 may be selected from materials common in the art, such as epoxy resins, and the like.

The invention also provides the use of the bistable display element described above in a reflective display device.

The beneficial effects are that: compared with the prior art, the bistable display element has the advantages that the metal layer is innovatively arranged on the public electrode of the bistable display element, and the metal layer and the public electrode are used as electrodes to transmit signals, so that the impedance effect of the public electrode is reduced, and the delay problem in the signal transmission process is solved; more importantly, because the impedance effect is weakened, the alternating voltage required for driving the bistable display is correspondingly reduced, so that the same working state can be realized by only releasing lower alternating voltage by using a driving IC chip of the bistable display device, and the research and development cost of the bistable display device is greatly reduced.

Drawings

Fig. 1: a drive waveform for a common bistable display element;

fig. 2: a cross-sectional schematic of the bistable display element of the invention;

fig. 3: the invention relates to a layout schematic diagram of a metal layer in a bistable display element;

fig. 4: the driving waveform of the bistable display element;

Wherein: 200: a bistable display element; 201: a first substrate base plate; 202: a common electrode; 203: a black matrix; 204: a metal layer; 205: an electrochromic layer; 206: charged particles; 207: sealing; 208: a pixel electrode; 209: a second substrate.

Detailed Description

In the following text, the dimensions (e.g., length, width, thickness and depth) of elements (e.g., layers, films, substrates, regions, etc.) in the drawings are exaggerated in unequal proportions for clarity in the technical features of the present disclosure. Accordingly, the description and illustrations of the embodiments below are not limited to the dimensions and shapes presented by the elements of the drawings, but are intended to cover deviations in the dimensions, shapes, and both, as a result of actual processes and/or tolerances. For example, the planar surface shown in the figures may have rough and/or non-linear features, while the acute angles shown in the figures may be rounded. Accordingly, the elements presented in the drawings are intended to be schematic, and are not intended to accurately depict the actual shape of the elements, nor to limit the claims. Furthermore, the number of at least one element in the drawings may be significantly smaller than in actual cases, so that the description and explanation of the embodiments below is not limited to the number of elements in the drawings.

Further, the terms "about," "approximately" or "substantially" as used herein encompass not only the explicitly recited values and ranges of values, but also the allowable ranges of deviation as would be understood by one of ordinary skill in the art, wherein the range of deviation is determined by the error in the measurement, such as due to limitations in both the measurement system or process conditions. Further, "about" may mean within one or more standard deviations of the above values, for example: within ±30%, ±20%, ±10% or ±5%. The terms "about," "approximately" or "substantially" as used herein may be used to select an acceptable range of deviations or standard deviations based on optical, etching, mechanical or other properties, and not to cover all of these with a single standard deviation.

Referring to fig. 2, a bistable display element 200 provided by the present invention includes a first substrate 201, a second substrate 209, and an electrochromic layer 205 encapsulated therebetween. A common electrode 202 and a metal layer 204 are sequentially arranged on one side of the first substrate 201 close to the electrochromic layer; electrochromic layer 205 includes charged particles 206; a pixel electrode 208 is arranged on one side of the second substrate 209 close to the electrochromic layer 205; an encapsulant 207 encapsulating the electrochromic layer 205 is disposed between the first substrate 201 and the second substrate 209. It should be noted that the above description of "provided with" or "provided with" does not necessarily limit that the two are brought into contact.

In this embodiment, the first substrate 201 is a transparent substrate, and the material of the first substrate may be a rigid substrate, such as a glass plate or a PMMA substrate, or may be a flexible substrate, such as a substrate made of PI or PET as a main component. In addition to the above-exemplified materials, the first substrate 201 may be a rigid substrate or a flexible substrate made of other materials. Here, the constituent materials of the first substrate 201 are not limited to the materials exemplified above.

In the present embodiment, the second substrate 209 may be the same as the first substrate 201, that is, the second substrate 209 may be a transparent substrate, and may be the above-mentioned rigid substrate (e.g., glass plate or PMMA substrate) or flexible substrate (PI substrate or PET substrate). However, in other embodiments, the second substrate 209 may also be an opaque substrate, for example, the second substrate 209 may be one of a black opaque PMMA substrate, PI substrate, or PET substrate.

In this embodiment, in order to shield the light leakage portion on the first substrate 201, a black matrix 203 is further disposed between the first substrate 201 and the common electrode 202, and the region of the black matrix 203 formed on the first substrate 201 should also correspond to other regions than the electrode region of the portion of the pixel electrode 208 that is not the storage capacitor electrode. Generally, the black matrix 203 forms a mesh structure on the first substrate base 201.

In this embodiment, the electrochromic layer 205 contains charged particles 206 in the form of microcapsules. In other embodiments, the form of the charged particles 206 may be any one or more combinations of micro-cups, rotating balls, etc. as will occur to those of skill in the art depending on the needs of the actual application. Further, the electrochromic layer 205 further includes a dispersion medium (not shown), and the dispersion medium may be a mixed solution of tetrachloroethylene and toluene, which is a well-known choice to those skilled in the art. The charged particles 206 may contain therein charged color particles, for example, at least one of red particles, green particles, blue particles, black particles, white particles, and the like, according to the demand of the display effect. When the bistable electrophoretic display device performs color display, corresponding driving voltages are applied to the common electrode 202 of the first substrate 201 and the pixel electrode 208 on the second substrate 209, and the charged particles 206 with different colors are directed to one side of the display according to the direction of the electric field under the action of the electric field, so that external light irradiated to the charged particles is reflected. It should be noted that the foregoing description is merely illustrative, and is convenient for understanding the display principle of the bistable display element 200 in different situations, and the specific selection of the substances contained in the electrochromic layer 205 may be performed according to the knowledge of those skilled in the art, and the same kind of the descriptions are not limited herein.

In other embodiments, any one or more combinations of cholesteric liquid crystal molecules, nematic liquid crystal molecules, or smectic liquid crystal molecules may also be included in electrochromic layer 205. The three liquid crystal molecules, cholesteric, smectic and nematic liquid crystal molecules, differ structurally: 1) Cholesteric liquid crystal molecules are in a flat shape, the molecules are arranged into layers, the long axes of the molecules in the layers are parallel to the plane of the layers, and the long axes of the molecules in different layers are arranged into a spiral structure along the normal direction of the layers, and can be divided into a left-handed structure and a right-handed structure; 2) Smectic phase liquid crystal molecules and layers of the molecules are obliquely arranged, the molecular structure contains asymmetric chiral groups, a torsion spiral structure can be formed, and the smectic phase liquid crystal is a positive biaxial crystal; 3) The nematic liquid crystal is composed of rod-like molecules, is approximately parallel to be oriented, has one-dimensional orientation order, is not layered in molecular arrangement, can slide up and down, left and right, front and back, has low order degree and low viscosity. But the three structures are the same in that: all of which are elongated and rigid and have dielectric anisotropy and optical anisotropy, so that the three liquid crystal molecules can change arrangement modes under the action of an electric field formed between the first substrate 201 and the second substrate 209, thereby realizing different display effects.

It should be noted that the potential difference generated between the first substrate 201 and the second substrate 209 may be adjusted by an external control element (not shown) electrically connected to the common electrode 202 and the pixel electrode 208, for example, a timing controller or a processor.

In this embodiment, the common electrode 202 and the pixel electrode 208 are made of the same material, and may be transparent conductive materials, which may be Transparent Conductive Oxide (TCO) or conductive polymer, such as ITO, IZO, PEDOT. The material of the black matrix 203 may be black chrome or carbon black, which is a material commonly used in the art. The material of the metal layer 204 may be common metals such as aluminum and copper or alloys thereof, and the material with a resistance smaller than that of the common electrode 202 is selected as the material of the metal layer 204.

On the first substrate 201 provided with the black matrix 203, when the metal layer 204 is formed on the common electrode 202, the area occupied by the metal layer 204 is not larger than the area formed by the black matrix 203, so as not to reduce the light transmittance of the bistable display element 200. If the black matrix 203 is in a network structure on the first substrate 201, the metal layer 204 may be formed in a network structure on the common electrode 202, or may be disposed in other shapes in a network region formed by the black matrix 203. In addition, the area formed by the metal layer 204 is not larger than the area formed by the black matrix 203, so that the shielding of the metal layer 204 to light is avoided, and the display effect of the bistable display element 200 is not affected.

In some embodiments, the bi-stable display element 200 is prepared according to the following steps:

S1: providing a first substrate 201, and forming a common electrode 202 on the first substrate 201; providing a second substrate 209, and forming a pixel electrode 208 on the second substrate 209;

s2: forming a metal layer 204 on the common electrode 202, the metal layer 204 and the common electrode 202 together being used as electrodes for signal transmission;

S3: and packaging the charged particles 206 in a sealed space formed by the first substrate 201, the second substrate 209 and the sealing compound 207 through a filling process to form an electrochromic layer 205, thus obtaining the bistable display element 200.

In this embodiment, the first substrate 201 is provided with the black matrix 203, and the process of preparing the bistable display element 200 includes the following steps:

S1: providing a first substrate 201, and forming a black matrix 203 on the first substrate 201; providing a second substrate 209, and forming a pixel electrode 208 on the second substrate 209;

S2: forming a common electrode 202 on the first substrate base 201 and the black matrix 203;

S3: forming a metal layer 204 on the common electrode 202 in a region corresponding to the black matrix 203, the metal layer 204 together with the common electrode 202 being used as an electrode for signal transmission;

s4: and packaging the charged particles 206 in a sealed space formed by the first substrate 201, the second substrate 209 and the sealing compound 207 through a filling process to form an electrochromic layer 205, thus obtaining the bistable display element 200.

In other embodiments, the substance contained in the electrochromic layer 205 may be cholesteric liquid crystal molecules and/or nematic liquid crystal molecules and/or smectic liquid crystal molecules, and in this case, the bistable display element 200 is used as a bistable liquid crystal display element, and the preparation process is based on the above preparation process, and the charged particles 206 are replaced with cholesteric liquid crystal molecules and/or nematic liquid crystal molecules and/or smectic liquid crystal molecules, so as to obtain the bistable liquid crystal display element.

In this embodiment, the common electrode 202 and the pixel electrode 208 are patterned films, which may be formed by thin film deposition and photolithography, wherein the common electrode 202 may include a plurality of upper conductive strips in parallel, and the pixel electrode 208 may include a plurality of lower conductive strips in parallel. The upper conductive strips may extend in a longitudinal direction and the lower conductive strips may extend in a transverse direction such that the upper and lower conductive strips are staggered with respect to each other to present a net-like distribution. When a potential difference (i.e., voltage) is generated between the first substrate 201 and the second substrate 209 due to the electrification, the electrochromic layer 205 generates an electric field, and the color plane orientation of the charged particles 206 is changed by adjusting the voltage, so as to realize the display effect of different colors.

In this embodiment, the bistable display element 200 further comprises an encapsulant 207, wherein the encapsulant 207 is located between the first substrate 201 and the second substrate 209 and connects the first substrate 201 and the second substrate 209. The encapsulant 207 can form a sealing layer around the electrochromic layer 205, so that the electrochromic layer 205 is sealed in the accommodating space defined by the first substrate 201, the second substrate 209 and the encapsulant 207, and the charged particles 206 are prevented from leaking out.

In the above-mentioned process of manufacturing the bistable display element 200, in order to achieve the problems of reducing impedance and solving signal delay, so as to achieve better technical effects, other component structures may be added to the bistable display element 200, or other kinds of substances may be selected, which is not strictly limited in the present invention.

In the present embodiment, the bistable display element 200 is assembled as an internal structure together with other support modules, circuit modules, etc. known to those skilled in the art to form a reflective display device. Illustratively, the driving voltages of the first substrate 201 and the second substrate 209 are set to an alternating voltage of ±15v by the circuit modules therein, respectively, at which time the electrochromic layer 205 is in an electric field with a voltage difference of 30V (see fig. 4). As a comparison, a bistable electrophoretic display device is selected, in which no metal layer is provided on the common electrode in the bistable electrophoretic display element, and in order to achieve the same display effect as that of the reflective display device formed by the bistable display element 200 in this embodiment when the alternating voltage is ±15v, the charged particles in the bistable display devices in the comparison group are adjusted to the same color plane orientation, and at this time, the bistable display devices in the comparison group need to be activated by a driving voltage of ±30v. Also, the voltage obtained on the common electrode of the bistable display element in the control group was 0V, and the voltage obtained on the pixel electrode was an alternating voltage of ±30v (see fig. 1). Meanwhile, the reflective display device including the bistable display element 200 has no apparent delay in performing an image update, and has a faster response speed compared to the bistable electrophoretic display device of the control group. Therefore, when the same display effect is achieved, the driving voltage required by the bistable display element provided by the invention can be smaller than that required by the bistable display device in the prior art, the impedance of the common electrode is weakened, and the signal delay problem is greatly relieved.

The present invention is not limited to the embodiments described above, but is not limited to the embodiments described above, and any simple modification, equivalent changes and modification made to the above embodiments according to the technical matter of the present invention can be made by those skilled in the art without departing from the scope of the technical solution of the present invention.

Claims (10)

1. A bistable display element comprising a first substrate and a second substrate disposed opposite each other, and an electrochromic layer disposed between the first substrate and the second substrate; the first substrate is provided with a common electrode and a metal layer on one side close to the electrochromic layer, and the second substrate is provided with a pixel electrode on one side close to the electrochromic layer.

2. The bistable display element of claim 1, wherein a black matrix is further provided on said first substrate.

3. The bistable display element of claim 2, wherein said black matrix is disposed between said first substrate base plate and said common electrode.

4. A bi-stable display element according to claim 3, wherein the metal layer is in a mesh structure over the common electrode.

5. The bistable display element of claim 4, wherein on said common electrode, said metal layer occupies an area that coincides with an area occupied by said black matrix, and said metal layer occupies an area that does not exceed an area occupied by said black matrix.

6. The bistable display element of claim 1, wherein the resistance of said metal layer is no greater than the resistance of said common electrode.

7. The bistable display element of claim 1, wherein said electrochromic layer is one of a charged particle layer or a liquid crystal molecular layer.

8. A process for the preparation of a bistable display element according to any of claims 1 to 7, characterized in that it comprises the following steps:

S1: providing a first substrate, and forming a black matrix on the first substrate; providing a second substrate, and forming a pixel electrode on the second substrate;

s2: forming a common electrode on the first substrate base plate;

s3: forming a metal layer on the common electrode, wherein the metal layer and the common electrode are used as electrodes for signal transmission;

S4: and packaging charged particles or liquid crystal molecules in a closed space formed by the first substrate, the second substrate and the sealing glue through a filling process to form an electrochromic layer, thus obtaining the bistable display element.

9. The process for preparing a bistable display element of claim 8, wherein in S3, the metal layer is formed by one of plasma sputtering, exposure and etching.

10. Use of a bistable display element according to any of claims 1-7 in a reflective display device.