CN102768429A - Double-sided cholesteric liquid crystal display and manufacturing method thereof - Google Patents

Abstract

The present disclosure relates to a double-sided cholesteric liquid crystal display, which includes: a first substrate with a first electrode on it; a second substrate with a second electrode on it and arranged opposite to the first electrode; A third electrode is located between the first electrode and the second electrode, and the first electrode, the second electrode, and the third electrode are electrically independent of each other; a first cholesteric liquid crystal layer is located on the first electrode and between the third electrode; a second cholesteric liquid crystal layer, located between the second electrode and the third electrode; a first light-absorbing layer, located between the first cholesteric liquid crystal layer and the third electrode between; and a second light-absorbing layer located between the second cholesteric liquid crystal layer and the third electrode. The present disclosure also relates to a method of manufacturing a double-sided cholesteric liquid crystal display.

Description

Double-sided cholesteric liquid crystal display and manufacturing method thereof

technical field

The present disclosure relates to cholesteric liquid crystal displays, and more particularly to a double-sided cholesteric liquid crystal display.

Background technique

A cholesteric liquid crystal display is a display technology that uses ambient light as a light source. Since it does not require a backlight module, it can reduce manufacturing costs. In addition, it has the advantages of high brightness, high contrast, energy saving, and no flicker, so it can be used outdoors, for example, in the manufacture of e-books.

Cholesteric liquid crystal has bistable characteristics, including planar state and focal conic state. Among them, the planar state is a reflective state, which can reflect light of a specific wavelength, and the specific wavelength of reflection can be adjusted by adjusting the concentration of optically active molecules in the cholesteric liquid crystal material. The focal conic state is a scattering state, and the light is scattered in all directions after passing through the liquid crystal molecules, and is absorbed by the light-absorbing layer behind, so there are bright and dark states.

At present, there is an urgent need to establish a better manufacturing method of cholesteric liquid crystal display in order to improve the reflectivity of the panel and protect the optical and electrical properties of the liquid crystal.

Contents of the invention

The object of the present invention is to provide a double-sided cholesteric liquid crystal display capable of improving the reflectivity of the panel.

Another object of the present invention is to provide a method for manufacturing a double-sided cholesteric liquid crystal display capable of improving panel reflectivity.

One embodiment of the present disclosure provides a double-sided cholesteric liquid crystal display, including: a first substrate with a first electrode on it; a second substrate with a second electrode on it, and the first electrode Relatively arranged; a third electrode, located between the first electrode and the second electrode, and the first electrode, the second electrode, and the third electrode are electrically independent from each other; a first cholesteric liquid crystal layer, located between the first electrode and the third electrode; a second cholesteric liquid crystal layer located between the second electrode and the third electrode; a first light absorbing layer located between the first cholesteric liquid crystal layer and the first cholesteric liquid crystal layer between the third electrodes; and a second light absorbing layer located between the second cholesteric liquid crystal layer and the third electrodes.

Yet another embodiment of the present disclosure provides a double-sided cholesteric liquid crystal display, including: a first substrate with a first electrode on it; a second substrate with a second electrode on it, and the first electrode oppositely disposed; a third electrode located between the first substrate and the second substrate, wherein the third electrode is disposed opposite to the first electrode; a fourth electrode located between the first substrate and the second substrate Between, wherein, the fourth electrode is arranged opposite to the second electrode, and the first electrode, the second electrode, the third electrode, and the fourth electrode are electrically independent from each other; a first cholesteric liquid crystal layer is located between the first electrode and the third electrode; and a second cholesteric liquid crystal layer located between the second electrode and the fourth electrode; a first light absorbing layer located between the third electrode and the first between the cholesteric liquid crystal layers; a second light absorbing layer located between the fourth electrode and the second cholesteric liquid crystal layer.

Another embodiment of the present disclosure provides a method for manufacturing a double-sided cholesteric liquid crystal display, including: providing a first substrate with a first electrode and a second substrate with a second electrode; A first cholesteric liquid crystal layer is formed on the first electrode; a first light-absorbing layer is formed on the first cholesteric liquid crystal layer; a third electrode is formed on the first light-absorbing layer; A second cholesteric liquid crystal layer is formed on the second electrode of the second cholesteric liquid crystal layer; a second light absorbing layer is formed on the second cholesteric liquid crystal layer; the first substrate and the second substrate are combined so that the first substrate The third electrode and the second light-absorbing layer of the second substrate face and stick together to form a double-sided cholesteric liquid crystal display.

Yet another embodiment of the present disclosure provides a method for manufacturing a double-sided cholesteric liquid crystal display, including: providing a first substrate with a first electrode and a second substrate with a second electrode; A first cholesteric liquid crystal layer is formed on the first electrode of the first liquid crystal; a first light-absorbing layer is formed on the first liquid crystal; a third electrode is formed on the first light-absorbing layer; a second electrode is formed on the second substrate Form a second cholesteric liquid crystal layer; form a second light-absorbing layer on the second cholesteric liquid crystal layer; form a fourth electrode on the second light-absorbing layer; pair the first and second substrates , and electrically insulate the third electrode from the fourth electrode to form a double-sided cholesteric liquid crystal display.

The advantages of the present invention are:

1) double-sided cholesteric liquid crystal display of the present invention is to coat the gelatin layer between the cholesteric liquid crystal layer and the light-absorbing layer, which can avoid the rupture of liquid crystal cells in the cholesteric liquid crystal layer, so that the cholesteric liquid crystal layer can It has high-density liquid crystal cells to improve reflectivity; in addition, it can also prevent the nano-pigment in the light-absorbing layer from entering the cholesteric liquid crystal layer, thereby maintaining the brightness of the display.

2) The present invention also uses the characteristics of different melting temperatures of gelatin at different humidity to bond two substrates to form a double-sided cholesteric liquid crystal display. Since each layer of the formed double-sided cholesteric liquid crystal display is laminated with gelatin, the relationship between voltage and reflectivity will not change after a period of time due to the difference in thermal expansion coefficient between the layers.

3) The double-sided cholesteric liquid crystal display of the present invention only uses three electrodes, so the manufacturing process cost can be reduced.

In order to make the features of the present disclosure more comprehensible, the preferred embodiments are listed below, together with the accompanying drawings, and are described in detail as follows:

Description of drawings

FIG. 1 shows a flowchart of the steps of manufacturing a double-sided cholesteric liquid crystal display according to one embodiment;

2-5 show cross-sectional views of each step of manufacturing a double-sided cholesteric liquid crystal display according to an embodiment;

Figure 6 shows the influence of humidity on the melting temperature of gelatin;

7 shows a cross-sectional view of a double-sided cholesteric liquid crystal display manufactured according to an embodiment;

Figures 8-9 show the distribution state of liquid crystal cells in the cholesteric liquid crystal layer;

Figure 10 shows a cross-sectional view of a double-sided cholesteric liquid crystal display manufactured according to an embodiment;

FIG. 11 shows a flow of steps for manufacturing a double-sided cholesteric liquid crystal display according to another embodiment;

12 shows a cross-sectional view of a double-sided cholesteric liquid crystal display manufactured according to another embodiment;

Figure 13 shows the effect of a gelatin layer on electrical properties according to one embodiment;

Figure 14 shows the effect of a gelatin layer on brightness according to one embodiment;

Figure 15 shows the effect of a gelatin layer on reliability according to one embodiment;

Fig. 16 shows a top view of a double-sided cholesteric liquid crystal formed according to an embodiment;

Among them, the main component symbol description

Detailed ways

Several different embodiments are presented according to different features of the present disclosure. The specific components and arrangements in the present disclosure are for simplicity, but the present disclosure is not limited to these embodiments. For example, a description of forming a first element on a second element may include embodiments in which the first element is in direct contact with the second element, as well as embodiments having additional elements formed between the first element and the second element such that the second element An embodiment in which one element is not in direct contact with a second element. In addition, for the sake of brevity, the present disclosure is represented by repeated element symbols and/or letters in different examples, but this does not mean that there is a specific relationship between the various embodiments and/or structures.

An embodiment of the present disclosure provides a method for manufacturing a double-sided cholesteric liquid crystal display, and the double-sided cholesteric liquid crystal display has three electrodes. FIG. 1 is a flow chart of manufacturing a double-sided cholesteric liquid crystal display according to an embodiment, and FIGS. 2-4 are cross-sectional views of a manufacturing process of a double-sided cholesteric liquid crystal display according to an embodiment.

Referring to FIG. 1 , step 102 provides a first substrate having a first electrode. Step 104 forms a first cholesteric liquid crystal layer on the first electrode of the first substrate. Step 106 forms a first light absorbing layer on the first cholesteric liquid crystal layer. Step 108 forms a third electrode on the first light absorbing layer. Step 110 provides a second substrate having a second electrode. Step 112 forms a second cholesteric liquid crystal layer on the second electrode of the second substrate. Step 114 forms a second light absorbing layer on the second cholesteric liquid crystal layer. In step 116 , the first substrate and the second substrate are assembled so that the third electrode and the second light-absorbing layer face and adhere to form a double-sided cholesteric liquid crystal display.

Please refer to the flow chart of FIG. 1 and the process sectional view of FIG. 2 at the same time. In step 102 , a first substrate 202 having a first electrode 201 is provided. In one embodiment, the first electrode may be indium tin oxide (ITO), gallium zinc oxide (GZO) or indium zinc oxide (IZO). The first substrate 202 may be a polyimide substrate (PI), a polyetheretherketone (PEEK) substrate, a polyethylene terephthalate (PET) substrate, a polycarbonate (PC) substrate or a glass substrate.

In step 104, a first cholesteric liquid crystal layer 204 is formed on the first electrode. The first cholesteric liquid crystal layer 204 preferably comprises cholesteric liquid crystal cells dispersed in gelatin. In one embodiment, the weight ratio of cholesteric liquid crystal cells to gelatin in the first cholesteric liquid crystal layer 204 is 1:12 to 12:1. In one embodiment, the first cholesteric liquid crystal layer 204 is coated by a roll-to-roll technique.

In step 106 , a first light absorbing layer 206 is formed on the first cholesteric liquid crystal layer 204 . In one embodiment, the first light absorbing layer 206 is coated by micro-nano roll printing technology. The first light-absorbing layer 206 can be obtained by mixing nano-scale pigments (nano pigments) into gelatin or field spreading nano-light-absorbing layer (Field Spreading Nano-pigment, FSN) added conductive particles, such as water-soluble conductive polymer Baytron P. Its absorption band can be selected from visible light region, ultraviolet light region, or infrared light region due to product design considerations. In one embodiment, the color of the first light absorbing layer 206 may be blue or red, but not limited thereto.

In step 108 , a third electrode 208 is formed on the first light absorbing layer 206 . In one embodiment, the third electrodes may be several strip electrodes. In another embodiment, the third electrode is a single plate electrode, which can be a silver electrode, a silver aluminum electrode, a copper electrode, a gold electrode, an indium tin oxide electrode (ITO), or an indium zinc oxide electrode (IZO) and other conductive materials. In one embodiment of the present disclosure, the third electrode is a silver electrode formed by screen printing.

Then, referring to FIGS. 1 and 3 , in step 110 , a second substrate 302 having a second electrode 301 is additionally provided. In one embodiment, the second electrode may be indium tin oxide (ITO), gallium zinc oxide (GZO) or indium zinc oxide (IZO). The second substrate 302 may be a polyimide substrate (PI), a polyetheretherketone (PEEK) substrate, a polyethylene terephthalate (PET) substrate, a polycarbonate (PC) substrate or a glass substrate.

In step 112, a second cholesteric liquid crystal layer 304 is formed on the second electrode. The second cholesteric liquid crystal layer 304 preferably comprises cholesteric liquid crystal cells dispersed in gelatin. In one embodiment, the weight ratio of cholesteric liquid crystal cells to gelatin in the second cholesteric liquid crystal layer 304 is 1:12 to 12:1.

In step 114 , a second light absorbing layer 306 is formed on the second cholesteric liquid crystal layer 304 . In one embodiment, the second light absorbing layer 306 is coated by micro-nano roll printing technology. The second light-absorbing layer 306 can be obtained by mixing nanoscale pigments into gelatin or adding conductive particles to the field-dispersed nano-light absorbing layer (FSN), such as water-soluble conductive polymer Baytron P. Its absorption band can be selected from visible light region, ultraviolet light region, or infrared light region due to product design considerations. In one embodiment, the color of the second light absorbing layer 306 can be blue or red, but not limited thereto.

Referring to FIGS. 1 and 4 , in step 116 , the first substrate 202 and the second substrate 302 are assembled so that the third electrode 208 and the second light absorbing layer 306 face each other to form a double-sided cholesteric liquid crystal display. That is, the first surface of the third electrode 208 is bonded to the first light-absorbing layer 206 , and the second surface opposite to the first surface is bonded to the second light-absorbing layer 306 to obtain a double-sided cholesteric liquid crystal display.

In one embodiment of the present disclosure, the method for assembling the first substrate 202 and the second substrate 302 can refer to FIG. The pairing of the second substrate 302 enables the third electrode 208 and the second light absorbing layer 306 to be bonded through the gelatin layer 212 . Wherein, the thickness of the gelatin layer 212 may range from 0.1 μm to 10 μm, and the weight ratio of gelatin in the gelatin layer 212 to gelatin and water may range from 0.1 wt % to 90 wt %. Alternatively, a gelatin layer can be coated on the second light-absorbing layer 306, and then the first substrate 202 and the second substrate 302 can be paired, so that the third electrode 208 and the second light-absorbing layer 306 can be pasted through the gelatin layer. Wherein, the coating method of the gelatin layer 212 may be to heat the dried gelatin layer to a melting temperature (for example, about 55° C.) to make it flowable, and then coat it. In another embodiment, the coating of the gelatin layer 212 may be performed by grinding dried gelatin into powder, and then coating by screen printing.

The above-mentioned method of assembling the two substrates does not use adhesives other than gelatin, so the formed double-sided cholesteric liquid crystal display has a relatively long-lasting color rendering ability. If the two substrates are assembled with other adhesives, the relationship between voltage and reflectivity (R-V curve) will change after a period of time due to the difference in thermal expansion coefficient of each layer, making it impossible to obtain the expected results when applying a specific voltage. , which means this monitor cannot render colors correctly. However, the present disclosure utilizes gelatin layer bonding, and since the composition of the cholesteric liquid crystal layer and the light-absorbing layer also includes the gelatin layer, there is no difference in coefficient of thermal expansion among the layers, and thus the relationship between voltage and reflectivity will not be changed.

In another embodiment of the present disclosure, the method for assembling the first substrate 202 and the second substrate 302 may be to directly heat the second light-absorbing layer 306 to melt the gelatin of the second light-absorbing layer 306, so when the first substrate 202 and the second substrate 302 When the second substrate 302 is paired, the second light-absorbing layer 306 can be sticky to the third electrode 208 . Wherein, the above-mentioned heating temperature may be 40°C to 140°C, and the heating time may be about 3 seconds to 10 seconds.

In yet another embodiment of the present disclosure, the method for assembling the first substrate 202 and the second substrate 302 may be to wet the second light-absorbing layer 306 with water. In one embodiment of the present disclosure, when the second light-absorbing layer is humidified with water, the water content of the second light-absorbing layer reaches 45% to 55%. As shown in Figure 6, the higher the water content in gelatin, the lower its melting temperature. Utilizing this property, the moisture content of the gelatin in the second light absorbing layer 306 can be increased by adding water, causing its melting temperature to decrease and thus become viscous. Then, for the set of the first substrate 202 and the second substrate 302 , the viscosity of the gelatin in the molten state is utilized, so that the second light absorbing layer 306 can have viscosity and be attached to the third electrode 208 . However, it should be noted that the amount of water in the humidification should not be too much, otherwise the moisture in the liquid crystal will be too heavy, and the melting temperature of the gelatin will drop, resulting in the melting and instability of the gelatin in the display, or causing the nano-pigments in the light-absorbing layer to enter the cholesterol. in the liquid crystal layer.

The above two methods of combining the two substrates do not use other adhesives, but use the properties of the gelatin in the second light-absorbing layer 306 for bonding. Because the melting temperature of gelatin will change with the water content in gelatin, the higher the water content in gelatin, the lower its melting temperature. Therefore, by heating the second light-absorbing layer to melt the gelatin therein to become viscous, or by adding water to lower the melting temperature of the gelatin in the second light-absorbing layer, it becomes easy to become molten and viscous. The second light absorbing layer 306 is bonded to the third electrode 208 . The above bonding does not require other adhesives, so the manufacturing process cost can be reduced, and since the bonding is made of gelatin, there is no difference in thermal expansion coefficient between the layers, and the relationship between voltage and reflectivity will not be changed. In one embodiment of the present disclosure, after the two substrates are pasted together, a water-blocking sealant can be coated around the two substrates to enhance their waterproof effect.

Both sides of the double-sided cholesteric liquid crystal display formed in an embodiment of the present disclosure can display images. For example, when an electric field is applied to the first electrode and the third electrode 208, the side of the first substrate 202 can display a first image. When an electric field is applied to the second electrode and the third electrode 208 , the side of the second substrate 302 can display a second image.

The above-mentioned double-sided cholesteric liquid crystal display has three electrodes, and by sharing the third electrode in the middle, electrode materials can be saved and process steps can be reduced, so the process cost can be reduced. In addition, since each display surface is independently controlled, sharing one electrode will not affect its operation, nor will it cause restrictions on use.

In addition, in another embodiment of the present disclosure, a gelatin layer can be formed between the cholesteric liquid crystal layer and the light-absorbing layer to protect the liquid crystal cells from being broken during the drying process. The formed structure can refer to the cross-section of FIG. 7 Figure, its formation steps are similar to Figure 1. However, after step 104 , it further includes forming a first gelatin layer 210 on the first cholesteric liquid crystal layer 204 , and then forming a first light absorbing layer 206 on the first gelatin layer 210 . In addition, after step 112 , the second gelatin layer 310 may be formed on the second cholesteric liquid crystal layer first, and then the second light-absorbing layer 306 is formed on the second gelatin layer 310 . The weight ratio of gelatin to gelatin and water in the first gelatin layer 210 and the second gelatin layer 310 may be 1 wt % to 90 wt %, respectively. Generally speaking, the thicknesses of the first gelatin layer 210 and the second gelatin layer 310 can be controlled within 0.5 μm to 10 μm.

Forming the first gelatin layer 210 and the second gelatin layer 310 can protect the liquid crystal cells from breaking during the drying process, but will not cause electrical damage to them. When manufacturing a cholesteric liquid crystal display, the thicker the cholesteric liquid crystal layer is, the higher the driving voltage will be. Therefore, the cholesteric liquid crystal layer has a certain thickness limit and cannot be thickened unconditionally. Generally, the thickness of the liquid crystal layer is between 3 μm and 20 μm. That is, if it is desired to increase the reflectivity of the liquid crystal, the proportion of the liquid crystal in the cholesteric liquid crystal layer should be increased on the premise of avoiding increasing the thickness of the liquid crystal. However, if the proportion of liquid crystal in the cholesteric liquid crystal layer is high, the liquid crystal cells in the cholesteric liquid crystal layer are likely to break during the drying process, resulting in that the reflectance of the display cannot be improved. As shown in FIG. 8 , it includes a substrate 802 , an electrode 801 , a cholesteric liquid crystal layer 804 , and a cholesteric liquid crystal microcell 814 . In one embodiment of the present disclosure, by forming the first and second gelatin layers on the first and second cholesteric liquid crystal layers, the liquid crystal in the cholesteric liquid crystal layer can be protected from being broken during the drying process, and the driving force cannot be caused. voltage rise. Referring to Fig. 9, the cholesteric liquid crystal layer 204 formed on the electrode 201 of the substrate 202, because of the protection of the gelatin layer 210 on it, can have more cholesteric liquid crystal cells 214 under the same thickness and will not When ruptured, the cholesteric liquid crystal cells 214 shown can achieve the closest packing in the cholesteric liquid crystal layer 204, thus achieving higher reflectivity. The weight ratio of liquid crystal to gelatin can be greater than 9.5:3.5, for example, between 1:12 and 12:1.

In addition, the use of the first and second gelatin layers can prevent the nano-pigments in the light-absorbing layer from entering the cholesteric liquid crystal layer, thereby maintaining the brightness of the display. Since the cholesteric liquid crystal layer and the light-absorbing layer are both soluble in gelatin, if the first and second gelatin layers are not provided, when the cholesteric liquid crystal layer and the light-absorbing layer are directly bonded, it may be due to the melting of the gelatin. However, the nano-pigments in the light-absorbing layer flow into the cholesteric liquid crystal layer, so that the color of the nano-pigments will appear when the cholesteric liquid crystal layer turns bright, thereby reducing the brightness of the display.

In one embodiment of the present disclosure, a gelatin layer is formed on the first and second cholesteric liquid crystal layers and the third electrode. Referring to Fig. 10, the double-sided cholesteric liquid crystal comprises first substrate 202, first electrode 201, first cholesteric liquid crystal layer 204, first gelatin layer 210, first light absorbing layer 206, third electrode 208, gelatin layer 212 , second light absorbing layer 306 , second gelatin layer 310 , second cholesteric liquid crystal layer 304 , second electrode 301 , and second substrate 302 . Among them, gelatin is used for bonding, so the relationship between the voltage and reflectivity will not be changed due to the difference in thermal expansion coefficient between the layers.

Another embodiment of the present disclosure provides a method for manufacturing a double-sided cholesteric liquid crystal display using four electrodes. FIG. 11 is a flow chart of manufacturing a double-sided cholesteric liquid crystal display, and FIG. 12 is a cross-sectional view of a double-sided cholesteric liquid crystal display.

Please refer to the flow chart of FIG. 11 and the process sectional view of FIG. 12 at the same time. Step 1102 provides a first substrate 202 with a first electrode 201 . Step 1104 forms a first cholesteric liquid crystal layer 204 on the first electrode 201 . Step 1105 forms a first gelatin layer 210 on the first cholesteric liquid crystal layer 204 . Step 1106 forms the first light absorbing layer 206 on the first gelatin layer 210 . Step 1108 forms the third electrode 208 on the first light absorbing layer 206 . The above step 1105 is an optional step.

Then, step 1110 provides a second substrate 302 with a second electrode 301 . Step 1112 forms a second cholesteric liquid crystal layer 304 on the second electrode 301 . Step 1113 forms a second gelatin layer 310 on the second cholesteric liquid crystal layer 304 . Step 1114 forms the second light absorbing layer 306 on the second gelatin layer 310 . Step 1116 forms the fourth electrode 308 on the second light absorbing layer 306 . Wherein step 1113 is an optional step. Step 1118 forms an insulating layer 316 on the fourth electrode 308 . The material of the insulating layer can be gelatin, polyvinyl alcohol (PVA), or adhesive material, and its formation method can be coating, pasting, or screen printing.

In step 1120, the first substrate 202 and the second substrate 302 are assembled so that the third electrode 208 and the fourth electrode 308 face to face, and are separated by the insulating layer 316 to form a double-sided cholesteric liquid crystal display. By providing an electric field to the electrodes, images can be displayed on both sides of the formed double-sided cholesteric liquid crystal display. For example, when an electric field is provided to the first electrode 201 and the third electrode 208 , the side of the first substrate 202 can display a first image. When an electric field is provided to the second electrode 301 and the fourth electrode 308 , the side of the second substrate 302 can display a second image.

For the above-mentioned first and second substrates, first and second light-absorbing layers, reference may be made to the foregoing embodiments. In addition, the above-mentioned third and fourth electrodes can be several strip-shaped electrodes or a single sheet-shaped electrode, which can be silver electrodes, silver-aluminum electrodes, copper electrodes, gold electrodes, indium tin oxide electrodes (ITO), or indium Conductive materials such as zinc oxide electrodes (IZO).

Although the present disclosure forms a gelatin layer between the first and second liquid crystal layers and the first and second light absorbing layers, those skilled in the art can replace the gelatin layers 210 and 310 with protective layers formed of other materials. For example, the protective layer may include a thermally cured adhesive layer, a polyvinyl alcohol (PVA) layer, or a combination of the foregoing. Therefore, the above changes or modifications do not deviate from the spirit and protection scope of the present disclosure.

[Example 1] Effect of Liquid Crystal Ratio on Reflectivity

In order to improve the reflectivity and reduce the driving voltage, in this embodiment, under the premise of not increasing the thickness of the cholesteric liquid crystal layer (avoiding the increase of the driving voltage due to the thickening of the cholesteric liquid crystal layer), the comparison of the cholesteric liquid crystal layer Effect of liquid crystal to gelatin ratio on reflectivity.

Using a polyethylene terephthalate (PET) substrate with indium tin oxide (ITO), the ITO is patterned into strips in the laser etching process; then the cholesteric liquid crystal layer, the gelatin layer, and the water-soluble conductive high The blue and red nano light absorbing layer (Nano-pigment, NP) of the molecular Baytron P is coated on it, and then the silver electrode is screen printed. The method of coating can utilize micro-nano roller printing technology. Among them, the cholesteric liquid crystal layer is that the liquid crystal cells reflecting 590nm light are evenly distributed in the gelatin, and its thickness is about 10 μm. The gelatin layer is formed by using 2wt% gelatin aqueous solution, and its thickness is about 1 μm; the light-absorbing layer is to dissolve nano-pigments in gelatin (the used nano-pigments are blue pigments of water-soluble conductive polymer Baytron P), and its thickness about 1 μm. After all the above steps were naturally dried at room temperature, the next step was carried out. When the weight ratio of liquid crystal molecules to gelatin in the cholesteric liquid crystal layer is changed, the reflectance thereof is shown in Table 1 below.

Table 1

The ratio of liquid crystal molecules to gelatin reflection wavelength Reflectivity 8:5 550nm 21.54% 9.5:3.5 550nm 22.08% 11:2 550nm 28.35%

It can be seen from Table 1 that the higher the weight ratio of liquid crystal molecules in the cholesteric liquid crystal layer, the higher the reflectivity thereof. Generally speaking, when the proportion of liquid crystal in the cholesteric liquid crystal layer is high, the liquid crystal cells are easy to break during the drying process of the cholesteric liquid crystal layer, so the reflectivity is often not as expected. However, in this embodiment, by coating a layer of gelatin layer on the cholesteric liquid crystal layer, the liquid crystal in the cholesteric liquid crystal layer can be prevented from cracking, thus having better reflectivity.

[Example 2] The impact of the gelatin layer on the electrical properties

Generally speaking, in order to increase the reflectivity of the liquid crystal and avoid the cracking of the liquid crystal, the thickness of the cholesteric liquid crystal layer must be increased, but at this time the driving voltage will also increase accordingly. The cholesteric liquid crystal display obtained in embodiment 1, by coating one layer of gelatin layer again on the cholesteric liquid crystal layer, when the ratio of liquid crystal molecules and gelatin contained in the cholesteric liquid crystal layer is large, the liquid crystal micells still cannot Cracks can have better reflectivity. The effect of this additional coated gelatin layer on electrical properties is investigated below.

FIG. 13 shows the relationship between the voltage and the reflectance of the liquid crystal display formed according to the steps described in Example 1, wherein the weight ratio of liquid crystal molecules to gelatin in the cholesteric liquid crystal layer is 11:2. Here, line A shows the result of forming a cholesteric liquid crystal layer with a total thickness of 10 μm by coating the cholesteric liquid crystal layer twice (first time 6 μm, second time 4 μm). Line B shows the result of forming a cholesteric liquid crystal layer with a total thickness of 11 μm by coating the cholesteric liquid crystal layer twice (first time 7 μm, second time 4 μm). Line C represents the result of coating a cholesteric liquid crystal layer twice (6 μm for the first time and 4 μm for the second time) and then coating a layer of gelatin (1 μm) to form a total thickness of 11 μm.

It can be seen from FIG. 13 that the additional gelatin layer (line C) will not cause the increase of its driving voltage.

[Example 3] Brightness test

This example shows the effect of adding a gelatin layer between the cholesteric liquid crystal layer and the light absorbing layer on the brightness of the cholesteric liquid crystal display. Wherein, the formation method of each layer of the cholesteric liquid crystal display is the same as that of Embodiment 1.

Figure 14 shows the average of the results of 20 repeated test pieces of displays with different structures. Among them, SC1 means that a cholesteric liquid crystal layer (the weight ratio of liquid crystal molecules to gelatin is 8:5), a light absorbing layer, and a silver electrode is sequentially formed on a PET/ITO substrate. SC2 means that a gelatin layer, a cholesteric liquid crystal layer (the weight ratio of liquid crystal molecules to gelatin is 8:5), a light absorbing layer, and a silver electrode are sequentially formed on the PET/ITO substrate. SC3 means that a cholesteric liquid crystal layer (the weight ratio of liquid crystal molecules to gelatin is 8:5), a gelatin layer, a light-absorbing layer, and a silver electrode are sequentially formed on a PET/ITO substrate. SC4 means that two layers of cholesteric liquid crystal layers are coated on the PET/ITO substrate in sequence (the weight ratio of liquid crystal molecules to gelatin is 8:5, and then a light-absorbing layer and silver electrodes are formed on the two layers of cholesteric liquid crystal layers. SC5 means that according to Sequentially form a cholesteric liquid crystal layer (liquid crystal molecule and gelatin weight ratio 9.5: 3.5), a gelatin layer, a light-absorbing layer, and a silver electrode on the PET/ITO substrate. Wherein, the thickness of the above-mentioned liquid crystal layer is about 13 μ m, and the thickness of the gelatin layer The thickness of the light-absorbing layer is about 1 μm, and the thickness of the silver electrode is about 14-20 μm.

It can be seen from Figure 14 that coating the gelatin layer (i.e. SC3 and SC5) between the cholesteric liquid crystal layer and the light-absorbing layer can prevent the nano-pigments in the light-absorbing layer from entering the cholesteric liquid crystal layer, causing the brightness of the display to decrease . Although SC4 has a second layer of cholesteric liquid crystal layer between the first layer of cholesteric liquid crystal layer and the light-absorbing layer, since the double layer of cholesteric liquid crystal layer will go through two drying processes, it will cause more liquid crystals. The microcells are broken and the brightness is reduced.

Figure 15 is the result of the reliability test. After the above-mentioned display was stored at 70° C. for 120 hours, the brightness and reflectance tests were carried out. Among them, the calculation method of the reliability percentage is as follows:

$\mathrm{<span\; class="notranslate">\; Rr</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Delta;R</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span>$

$\mathrm{<span\; class="notranslate">\; Lr</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span>$

Among them, Rr is the reflectivity reliability, ΔR is the reflectivity difference, and R is the initial reflectivity. Lr is the brightness reliability, ΔL is the brightness difference, and L is the initial brightness. It can be seen from the figure that after the gelatin layer is coated between the cholesteric liquid crystal layer and the light-absorbing layer, the brightness of the display remains almost 100% after being stored at 70°C for 120 hours, and its reflectivity only drops by 0-2 %.

[Example 4] Manufacturing method of double-sided cholesteric liquid crystal display

The design of this embodiment is mainly carried out towards three key points, including: the panel size should be close to A4 size, the resolution should reach 75dpi and the panel should have multi-color display.

First, a polyethylene terephthalate (PET) substrate with indium tin oxide (ITO) is used as the first substrate, which is about 120 cm long, 301.8 mm wide, and 178 μm thick.

Referring to Figure 16, 576 electrode areas are cut out on the first substrate with a laser cutting line at a resolution of 75dpi, a total of 3 groups of patterns. At this time, the ITO is patterned into strips, and then the coating process is performed.

The coating process is to cover the cholesteric liquid crystal layer, the gelatin layer, and the light-absorbing layer (Nano-pigment, NP) on the substrate by micro-nano roll printing technology. Among them, the cholesteric liquid crystal layer (9.5:3.5) is coated with two layers, and the liquid crystal cells reflecting 590nm light are evenly distributed in the gelatin, the first layer is about 6 μm, and the second layer is about 4 μm. The moisture content of the gelatin layer is about 2%, and its thickness is about 0.5 μm. The light-absorbing layer is a blue and red nano light-absorbing layer with a thickness of about 1 μm. In this embodiment, the light absorbing layer used is a Field Spreading Nano-pigmant (FSN) layer with conductive particles added to reduce the driving voltage of the panel.

After the above coating is dried, edge rubbing is performed to reduce the coated area to 102 mm below the center line of the substrate, so as to ensure that 8 mm of the auxiliary silver electrode area can be attached to the ITO. The silver electrode pattern is covered on the light absorbing layer, and the thickness of the silver electrode layer is about 20 μm. A total of 576 screen-printed silver electrodes are also screen-printed with a resolution of 75dpi, and a cross mark (about 5mm in length) is designed on the screen board to facilitate driving alignment, so as to facilitate subsequent driving of the panel. Among them, the horizontal line width of the silver electrode is about 150 μm; the line distance is about 188 μm; the line length is about 220 mm, and the left and right sides exceed the outermost edge laser by 7.249 mm. The straight line width of the silver electrode is about 90 μm; the line spacing is about 70 μm; the line length is about 10 mm.

Next, use another polyethylene terephthalate (PET) substrate with indium tin oxide (ITO) as the second substrate, and form a cholesteric liquid crystal layer, a gelatin layer, and blue and red layers in sequence according to the above method. The light-absorbing layer (Nano-pigment, NP). However, silver electrodes are not screen-printed on the light-absorbing layer.

Then, coat a layer of gelatin on the silver electrode on the first substrate, and then heat and press the first and second substrates (about 70-80° C., for a few seconds) to make the gelatin on the silver electrode and the second substrate The light-absorbing layers of the two electrodes are pasted together to obtain a cholesteric liquid crystal display capable of displaying on both sides. The driving frequency is 250HZ and the voltage is +/-100V. The formed double-sided cholesteric liquid crystal display is shown in Fig. 10, comprises first substrate 202, first electrode 201, first cholesteric liquid crystal layer 204, first gelatin layer 210, first light absorbing layer 206, third The electrode 208 , the gelatin layer 212 , the second light absorbing layer 306 , the second gelatin layer 310 , the second cholesteric liquid crystal layer 304 , the second electrode 301 , and the second substrate 302 .

In this embodiment, a gelatin layer is coated between the cholesteric liquid crystal layer and the light-absorbing layer, which can avoid the liquid crystal cells in the cholesteric liquid crystal layer from breaking, so that the liquid crystal cells in the cholesteric liquid crystal layer can have a high density, and Improve reflectivity. In addition, the nano-pigment in the light-absorbing layer can be prevented from entering into the cholesteric liquid crystal layer, thereby maintaining the brightness of the display. In addition, the characteristics of different melting temperatures of gelatin at different humidity are used to bond two substrates to form a double-sided cholesteric liquid crystal display. Since each layer of the formed double-sided cholesteric liquid crystal display is laminated with gelatin, the relationship between voltage and reflectivity will not change after a period of time due to the difference in thermal expansion coefficient between the layers. In addition, the double-sided cholesteric liquid crystal display formed in this embodiment only uses three electrodes, so the manufacturing cost can be reduced.

Although the present disclosure has been disclosed above with several preferred embodiments, it is not intended to limit the present disclosure, and anyone with ordinary knowledge in the technical field may make arbitrary changes without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the present disclosure should be determined by the scope defined by the appended claims.

Claims (29)

1. two-sided cholesteric liquid crystal display comprises:

One first substrate has one first electrode on it;

One second substrate has one second electrode on it, be oppositely arranged with this first electrode;

One third electrode, between this first electrode and this second electrode, and this first electrode, second electrode, and third electrode electrically independent each other;

One first cholesteric liquid crystal layers is between this first electrode and this third electrode;

One second cholesteric liquid crystal layers is between this second electrode and this third electrode;

One first light-absorption layer is between this first cholesteric liquid crystal layers and this third electrode; And

One second light-absorption layer is between this second cholesteric liquid crystal layers and this third electrode.

2. two-sided cholesteric liquid crystal display as claimed in claim 1, also comprise one first gelatin layer between this first cholesteric liquid crystal layers and this first light-absorption layer and/or one second gelatin layer between this second cholesteric liquid crystal layers and this second light-absorption layer.

3. two-sided cholesteric liquid crystal display as claimed in claim 1 also comprises a gelatin layer between this third electrode and this first light-absorption layer, perhaps between this third electrode and this second light-absorption layer.

4. two-sided cholesteric liquid crystal display as claimed in claim 1; Also comprise one first gelatin layer between this first cholesteric liquid crystal layers and this first light-absorption layer and/or one second gelatin layer between this second cholesteric liquid crystal layers and this second light-absorption layer, and a gelatin layer is between this third electrode and this first light-absorption layer or between this third electrode and this second light-absorption layer.

5. two-sided cholesteric liquid crystal display as claimed in claim 1, wherein this third electrode is several strip shaped electric poles.

6. two-sided cholesteric liquid crystal display as claimed in claim 1, wherein this third electrode is a sheet electrode.

7. two-sided cholesteric liquid crystal display as claimed in claim 1, wherein respectively do for oneself indium tin oxide ITO, gallium zinc oxide GZO or indium-zinc oxide IZO of this first or second electrode.

8. two-sided cholesteric liquid crystal display as claimed in claim 1, wherein respectively do for oneself pi substrate, polyetheretherketone substrate, polyethylene terephthalate substrate, polycarbonate substrate or glass substrate of this first or second substrate.

9. two-sided cholesteric liquid crystal display comprises:

One first substrate has one first electrode on it;

One second substrate has one second electrode on it, be oppositely arranged with this first electrode;

One third electrode, between this first substrate and this second substrate, wherein, this third electrode and this first electrode are oppositely arranged;

One the 4th electrode, between this first substrate and this second substrate, wherein, the 4th electrode and this second electrode are oppositely arranged, and this first electrode, second electrode, third electrode, and the 4th electrode electrically independent each other;

One first cholesteric liquid crystal layers is between this first electrode and this third electrode; And

One second cholesteric liquid crystal layers is between this second electrode and the 4th electrode;

One first light-absorption layer is between this third electrode and this first cholesteric liquid crystal layers;

One second light-absorption layer is between the 4th electrode and this second cholesteric liquid crystal layers.

10. two-sided cholesteric liquid crystal display as claimed in claim 9, also comprise one first gelatin layer between this first cholesteric liquid crystal layers and this first light-absorption layer and/or and one second gelatin layer between this second cholesteric liquid crystal layers and this second light-absorption layer.

11. two-sided cholesteric liquid crystal display as claimed in claim 9 comprises that also an insulation course is between this third electrode and the 4th electrode.

12. two-sided cholesteric liquid crystal display as claimed in claim 9; Also comprise one first gelatin layer between this first cholesteric liquid crystal layers and this first light-absorption layer and/or one second gelatin layer between this second cholesteric liquid crystal layers and this second light-absorption layer, and an insulation course is between this third electrode and the 4th electrode.

13. two-sided cholesteric liquid crystal display as claimed in claim 9, wherein respectively do for oneself indium tin oxide ITO, gallium zinc oxide GZO or indium-zinc oxide IZO of this first, second electrode.

14. two-sided cholesteric liquid crystal display as claimed in claim 9, wherein respectively do for oneself pi substrate, polyetheretherketone substrate, polyethylene terephthalate substrate, polycarbonate substrate or glass substrate of this first, second substrate.

15. the manufacturing approach of a two-sided cholesteric liquid crystal display comprises:

One first substrate with one first electrode and one second substrate with one second electrode are provided;

On first electrode of this first substrate, form one first cholesteric liquid crystal layers;

On this first cholesteric liquid crystal layers, form one first light-absorption layer;

On this first light-absorption layer, form a third electrode;

On second electrode of this second substrate, form one second cholesteric liquid crystal layers;

On this second cholesteric liquid crystal layers, form one second light-absorption layer;

To organizing this first substrate and this second substrate, make the third electrode of this first substrate and second light-absorption layer of this second substrate face and applying, to form a two-sided cholesteric liquid crystal display.

16. the manufacturing approach of two-sided cholesteric liquid crystal display as claimed in claim 15 also is included in and forms formation one second gelatin layer between one first gelatin layer and/or this second cholesteric liquid crystal layers and this second light-absorption layer between this first cholesteric liquid crystal layers and this first light-absorption layer.

17. the manufacturing approach of two-sided cholesteric liquid crystal display as claimed in claim 15 wherein to before organizing this first substrate and this second substrate, also is included in and forms an insulation course on this third electrode.

18. the manufacturing approach of two-sided cholesteric liquid crystal display as claimed in claim 15 wherein to before organizing this first substrate and this second substrate, also comprises this second light-absorption layer of heating.

19. the manufacturing approach of two-sided cholesteric liquid crystal display as claimed in claim 15 wherein to before organizing this first substrate and this second substrate, also comprises with this second light-absorption layer of water humidification.

20. the manufacturing approach of two-sided cholesteric liquid crystal display as claimed in claim 15, wherein this third electrode is several strip shaped electric poles.

21. the manufacturing approach of two-sided cholesteric liquid crystal display as claimed in claim 15, wherein this third electrode is a sheet electrode.

22. the manufacturing approach of two-sided cholesteric liquid crystal display as claimed in claim 15, wherein respectively do for oneself indium tin oxide ITO, gallium zinc oxide GZO or indium-zinc oxide IZO of this first, second electrode.

23. the manufacturing approach of two-sided cholesteric liquid crystal display as claimed in claim 15, wherein respectively do for oneself pi substrate, polyetheretherketone substrate, polyethylene terephthalate substrate, polycarbonate substrate or glass substrate of this first or second substrate.

24. the manufacturing approach of a two-sided cholesteric liquid crystal display comprises:

One first substrate with one first electrode and one second substrate with one second electrode are provided;

On first electrode of this first substrate, form one first cholesteric liquid crystal layers;

On this first liquid crystal, form one first light-absorption layer;

On this first light-absorption layer, form a third electrode;

On second electrode of this second substrate, form one second cholesteric liquid crystal layers;

On this second cholesteric liquid crystal layers, form one second light-absorption layer;

On this second light-absorption layer, form one the 4th electrode;

To organizing this first, second substrate, and make this third electrode and the 4th electrode be electrically insulated, to form a two-sided cholesteric liquid crystal display.

25. the manufacturing approach of two-sided cholesteric liquid crystal display as claimed in claim 24 also is included in and forms formation one second gelatin layer between one first gelatin layer and/or this second cholesteric liquid crystal layers and this second light-absorption layer between this first cholesteric liquid crystal layers and this first light-absorption layer.

26. the manufacturing approach of two-sided cholesteric liquid crystal display as claimed in claim 24 wherein to before organizing this first substrate and this second substrate, also is included in and forms an insulation course on this third electrode or the 4th electrode.

27. the manufacturing approach of two-sided cholesteric liquid crystal display as claimed in claim 24, wherein respectively do for oneself several strip shaped electric poles or a sheet electrode of the 3rd, the 4th electrode.

28. the manufacturing approach of two-sided cholesteric liquid crystal display as claimed in claim 24, wherein respectively do for oneself indium tin oxide ITO, gallium zinc oxide GZO or indium-zinc oxide IZO of this first, second electrode.

29. the manufacturing approach of two-sided cholesteric liquid crystal display as claimed in claim 24, wherein this first or second substrate comprises pi substrate, polyetheretherketone substrate, polyethylene terephthalate substrate, polycarbonate substrate or glass substrate separately.

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