CN215729181U

CN215729181U - PDLC display

Info

Publication number: CN215729181U
Application number: CN202121626157.7U
Authority: CN
Inventors: 余荣; 黄琛; 金小莉; 吕岳敏; 杨烨
Original assignee: Shantou Goworld Display Plant Ii Co ltd; Shantou Goworld Display Technology Co Ltd
Current assignee: Shantou Goworld Display Plant Ii Co ltd; Shantou Goworld Display Technology Co Ltd
Priority date: 2021-07-17
Filing date: 2021-07-17
Publication date: 2022-02-01
Anticipated expiration: 2031-07-17

Abstract

The utility model relates to a PDLC display, which comprises a liquid crystal box and a liquid crystal layer, wherein the liquid crystal box comprises a first substrate and a second substrate which are bonded with each other, the liquid crystal layer is clamped between the first substrate and the second substrate, the inner side surfaces of the first substrate and the second substrate are respectively provided with a first electrode and a second electrode, and the first electrode and the second electrode have an overlapping area; the liquid crystal layer comprises a first liquid crystal compound and a second liquid crystal compound which are mixed with each other, the first liquid crystal compound is solidified liquid crystal, and liquid crystal molecules of the first liquid crystal compound have fixed first orientation; the second liquid crystal compound is liquid crystal in a fluid state, and liquid crystal molecules of the second liquid crystal compound have a second orientation. The PDLC display not only can reduce the driving voltage required by a liquid crystal layer and reduce the design difficulty of a driving circuit, but also can realize the display mode of white characters under the condition of setting a black background, and has a wider application range.

Description

PDLC display

Technical Field

The utility model relates to the field of displays, in particular to a PDLC display.

Background

Pdlc (polymer dispersed liquid crystal), also known as polymer dispersed liquid crystal, is a liquid crystal structure that disperses fluid liquid crystals within a solid polymer. The PDLC display (also called polymer dispersed liquid crystal display) made of PDLC can realize the conversion between transparent and turbid display states by controlling the light scattering of the liquid crystal, does not need to stick a polaroid, and has a simpler structure than a common liquid crystal display.

In the conventional PDLC display, the liquid crystal layer generally includes independent liquid crystal droplets completely enclosed by a polymer, and the polymer is a transparent photosensitive resin, and in the back area of the display and the OFF-state display area (such as a pixel or a pen segment) where the driving voltage is zero (or lower), the liquid crystal molecules in the liquid crystal droplets are randomly oriented (i.e. the arrangement direction of the liquid crystal molecules) when contacting the polymer, so that the optical axes of the liquid crystal droplets consistent with the liquid crystal molecule orientation are very disordered, and the liquid crystal layer has scattering and reflecting effects on the transmitted light to make the above-mentioned area appear cloudy (such as milky cloudy); in the ON state display region with sufficient voltage applied, the optical axes of the liquid crystal droplets are uniform under the action of the electric field, which can effectively reduce or eliminate the scattering and reflection of light by the liquid crystal layer, so that the liquid crystal layer is in a clear transparent state, which can be in a background color (e.g. black) when the background (e.g. black background) is padded. However, the liquid crystal layer of the PDLC display generally uses a large proportion of photosensitive resin to seal the liquid crystal into independent droplets (to avoid mutual connection of the liquid crystal and mutual influence of the orientations), and the PDLC display needs to have enough liquid crystal droplets in order to ensure the turbidity degree of the OFF-state display area, so the liquid crystal layer needs to be made very thick (>20 μm), which results in very high driving voltage, making the design of the driving circuit difficult, and the back substrate area of the PDLC display is in a turbid state, which generally can only realize the display mode of black-on-white characters, but cannot realize the display mode of black-on-white characters, thus limiting the application range of the PDLC display.

SUMMERY OF THE UTILITY MODEL

The technical problem to be solved by the utility model is to provide a PDLC display, which not only can reduce the driving voltage required by a liquid crystal layer and reduce the design difficulty of a driving circuit, but also can realize a display mode of white characters on a black background under the condition of setting a black background, and has a wider application range. The technical scheme is as follows:

the utility model provides a PDLC display, includes liquid crystal cell and liquid crystal layer, and the liquid crystal cell includes first base plate and the second base plate of mutual bonding, and the liquid crystal layer presss from both sides and establishes between first base plate and second base plate, and the medial surface of first base plate, second base plate is equipped with first electrode, second electrode respectively, and first electrode, second electrode have overlap region, its characterized in that: the liquid crystal layer comprises a first liquid crystal compound and a second liquid crystal compound which are mixed with each other, the first liquid crystal compound is solidified liquid crystal, and liquid crystal molecules of the first liquid crystal compound have fixed first orientation; the second liquid crystal compound is liquid crystal in a fluid state, and liquid crystal molecules of the second liquid crystal compound have a second orientation.

In the PDLC display, the second liquid crystal compound and the first liquid crystal compound are in intermixed contact with each other, and the first liquid crystal compound has an alignment effect on liquid crystal molecules of the second liquid crystal compound. In a natural state (i.e., no voltage is applied to the first electrode and the second electrode and no electric field is present), the liquid crystal molecules of the first liquid crystal compound and the second liquid crystal compound have uniform orientation, and an OFF state display region is observed to be a clear transparent state; because the first liquid crystal compound and the second liquid crystal compound have consistent orientation in a natural state, the first liquid crystal compound does not need to seal the second liquid crystal compound into liquid crystal microdroplets, the proportion of the second liquid crystal compound can be greatly improved, so that the effect of an electric field on the liquid crystal layer is very sensitive, and the driving voltage required by the liquid crystal layer is lower. When sufficient voltage is applied to the first electrode and the second electrode, an electric field is formed in the liquid crystal layer in the overlapping area, the orientation of the first liquid crystal compound is unchanged, the second orientation of each liquid crystal molecule of the second liquid crystal compound deviates from the first orientation along with the change of the electric field, so that the second orientation is inconsistent with the first orientation (the liquid crystal molecules close to the first liquid crystal compound in the second liquid crystal compound are deflected relatively little, and the liquid crystal molecules far away from the first liquid crystal compound are deflected relatively much), when light passes through the liquid crystal layer, the light needs to pass through liquid crystal media with different orientations, the refractive indexes of the liquid crystal media with different orientations are generally different ON the propagation path of the light, the light can be scattered or reflected, and an ON state display area can be observed to be in an opaque turbid state. The OFF state display area of the PDLC display is in a transparent state, and the ON state display area is in a turbid state, so that the driving voltage required by the liquid crystal layer can be reduced, the design difficulty of a driving circuit is reduced, and the display mode of white characters ON a black background can be realized under the condition of setting a black background, so that the PDLC display has a wider application range.

Generally, the first substrate and the second substrate are transparent glass substrates or transparent plastic substrates; the thickness of the transparent glass substrate can be 0.3-2 mm; the transparent plastic substrate can be a PET plastic sheet or a CPI film; the first substrate and the second substrate are bonded through a sealing rubber ring to form sealing for the liquid crystal layer; and spacers (such as spacer balls) for maintaining the thickness of the liquid crystal layer (generally 3-10 μm) are arranged between the first substrate and the second substrate.

In a preferred embodiment, the first liquid crystal compound includes a plurality of segments of linear bodies, the plurality of segments of linear bodies are arranged in an ordered or disordered state and are connected to each other, and the second liquid crystal compound is filled in a space other than the first liquid crystal compound.

In a further preferred embodiment, the plurality of segments of the thread-like body are interlaced into a honeycomb structure, the honeycomb structure has a plurality of holes, and the second liquid crystal compound is filled in the holes of the honeycomb structure formed by the first liquid crystal compound.

In a further preferred embodiment, the size of the pores is 0.2 μm to 2 μm. Thus, the first liquid crystal compound and the second liquid crystal compound can be fully mixed, and the light scattering property of the opaque liquid crystal layer can be improved.

In a further preferred embodiment, the volume ratio of the first liquid crystal compound to the second liquid crystal compound is 0.02 to 0.1: 1. when the first liquid crystal compound and the second liquid crystal compound have the above volume ratio, the main component of the liquid crystal layer is the second liquid crystal compound, and the occupation ratio of the second liquid crystal compound is large, so that the effect of an electric field on the liquid crystal layer is very sensitive, and in an actual device, the driving voltage required by the liquid crystal layer is lower (for example, below 10V).

In a preferred embodiment, the first electrode and the second electrode are transparent conductive layers formed by patterning transparent conductive films, and the transparent conductive layers have outer connection ends extending out of the liquid crystal layer. The transparent conductive film can be an ITO film and is patterned through photoetching; the overlapping area between the first electrode and the second electrode can be made into the pattern of pixels or pen segments; the external terminals of the first electrode and the second electrode are used for applying voltage or driving signals.

In a preferred embodiment, the first liquid crystal compound and the second liquid crystal compound are nematic liquid crystals having birefringence or compounds thereof; the first liquid crystal compound and the second liquid crystal compound have optical axes consistent with the liquid crystal molecular orientation, and the first liquid crystal compound and the second liquid crystal compound respectively have a first refractive index and a second refractive index in a direction parallel to the optical axes and a direction perpendicular to the optical axes. Typically, the first refractive index is greater than the second refractive index.

In order to maintain the transparency of the liquid crystal layer in a natural state, it is more preferable that the second refractive index of the second liquid crystal compound is the same as the second refractive index of the first liquid crystal compound.

In order to provide the liquid crystal layer with better transparency, it is further more preferable that the first refractive index of the second liquid crystal compound is the same as the first refractive index of the first liquid crystal compound. The first refractive index and the second refractive index of the first liquid crystal compound obtained by curing the liquid crystal are easily set to be consistent with those of the second liquid crystal compound (the required refractive index can be easily obtained by a common liquid crystal blending method), the orientation and the optical axis of the first liquid crystal compound and the second liquid crystal compound are also kept consistent in a natural state, and the back bottom area and the OFF display area of the liquid crystal display are in a clear transparent state.

Typically, the first liquid crystal compound is a positive liquid crystal, a neutral liquid crystal, or a negative liquid crystal; the second liquid crystal compound is a positive liquid crystal whose liquid crystal molecules tend to be parallel to an electric field when subjected to the electric field.

In a preferred embodiment, the first liquid crystal compound is formed by curing liquid crystal molecules aligned in advance through a cross-linking reaction. The liquid crystal molecules of the first liquid crystal compound may be nematic liquid crystal molecules modified with unsaturated groups (for example, -CH = CH2) at the ends, and in the manufacturing process, a photosensitizer may be added to the liquid crystal, the liquid crystal is disposed between the first substrate and the second substrate to form a liquid crystal layer (which may be disposed by a common method for liquid crystal displays such as vacuum infusion and drip irrigation), and then ultraviolet light is irradiated to cause the liquid crystal molecules of the first liquid crystal compound to undergo a cross-linking reaction and be cured. Before the first liquid crystal compound is cured, the liquid crystal layer has a certain orientation (such as horizontal orientation or vertical orientation, specifically related to the materials of the inner surfaces of the first substrate and the second substrate (the orientation can be further stabilized by a process such as heating and re-aligning), when the first liquid crystal compound is cured, the orientation is fixed in the first liquid crystal compound (and is not affected by an electric field subsequently), and the second liquid crystal compound is affected by the inner surfaces of the first substrate and the second substrate and the first liquid crystal compound, and can keep a uniform orientation in a natural state.

In the case where the second liquid crystal compound is a positive liquid crystal, the first liquid crystal compound and the second liquid crystal compound are preferably horizontally aligned. More preferably, the inner side surfaces of the first substrate and the second substrate are both provided with a horizontal alignment layer. In a further more preferred embodiment, the horizontal alignment layer is a horizontal alignment polyimide coating.

The liquid crystal layer of the PDLC display is formed by mixing a first liquid crystal compound and a second liquid crystal compound, wherein the first liquid crystal compound is solidified liquid crystal, and liquid crystal molecules of the first liquid crystal compound have fixed first orientation; the second liquid crystal compound is liquid crystal in a fluid state, and liquid crystal molecules of the second liquid crystal compound have a second orientation; the first liquid crystal compound and the second liquid crystal compound have consistent orientation in a natural state (namely, no voltage is applied to the first electrode and the second electrode and no electric field exists), so that an OFF state display area is in a clear transparent state; because the first liquid crystal compound and the second liquid crystal compound have consistent orientation in a natural state, the first liquid crystal compound does not need to seal the second liquid crystal compound into liquid crystal microdroplets, the proportion of the second liquid crystal compound can be greatly improved, so that the effect of an electric field on the liquid crystal layer is very sensitive, and the driving voltage required by the liquid crystal layer is lower. When sufficient voltage is applied to the first electrode and the second electrode to generate an electric field, the orientation of the first liquid crystal compound is unchanged, and the second orientation of each liquid crystal molecule of the second liquid crystal compound deviates from the first orientation along with the change of the electric field, so that the second orientation is inconsistent with the first orientation, an ON state display area can be in a turbid state, the driving voltage required by the liquid crystal layer can be reduced, the design difficulty of a driving circuit is reduced, and in addition, under the condition of setting a black background, the display mode of black and white characters can be realized, and the wide application range is realized.

Drawings

Fig. 1 is a schematic structural diagram of a PDLC display according to a preferred embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view of fig. 1.

Fig. 3 is a schematic diagram of the structure of the first liquid crystal compound in the PDLC display of fig. 1.

Fig. 4 is a reaction scheme of liquid crystal molecules of the first liquid crystal compound of fig. 3 and curing thereof.

Fig. 5 is a schematic diagram of the liquid crystal alignment of the OFF state display region in the PDLC display of fig. 1.

Fig. 6 is a schematic diagram of the liquid crystal alignment of the ON state display region in the PDLC display of fig. 1.

Detailed Description

As shown in fig. 1 to 6, the PDLC display includes a liquid crystal cell 1 and a liquid crystal layer 2, the liquid crystal cell 1 includes a first substrate 11 and a second substrate 12 bonded to each other, the liquid crystal layer 2 is sandwiched between the first substrate 11 and the second substrate 12, a first electrode 13 and a second electrode 14 are respectively disposed on inner side surfaces of the first substrate 11 and the second substrate 12, an overlapping region 15 exists between the first electrode 13 and the second electrode 14, and when a voltage is applied to the first electrode 13 and the second electrode 14, an electric field is formed in the liquid crystal layer 2 in the overlapping region 15; the liquid crystal layer 2 comprises a first liquid crystal compound 21 and a second liquid crystal compound 22 which are mixed with each other, the first liquid crystal compound 21 is a solidified liquid crystal, and liquid crystal molecules of the first liquid crystal compound 21 have a fixed first orientation; the second liquid crystal compound 22 is a liquid crystal in a fluid state, and liquid crystal molecules of the second liquid crystal compound 22 have a second orientation; the second orientation is consistent with the first orientation when no voltage is applied to the first and

second electrodes

13 and 14 and no electric field is present, and the second orientation deviates from the first orientation as the electric field changes when the voltage is applied to the first and

second electrodes

13 and 14 to generate the electric field.

In this embodiment, the first substrate 11 and the second substrate 12 are transparent glass substrates or transparent plastic substrates (the transparent plastic substrates may be PET plastic sheets or CPI films); the thickness of the transparent glass substrate is 0.3-2 mm; the thickness of the liquid crystal layer 2 is 3-10 μm; the first substrate 11 and the second substrate 12 are bonded by a seal rubber 16 to form a seal for the liquid crystal layer 2.

In this embodiment, the first liquid crystal compound 21 includes a plurality of segments 211, the segments 211 are arranged in an ordered or disordered state and are interlaced into a honeycomb structure, the honeycomb structure has a plurality of holes 212, the size of the holes 212 is 0.2 μm to 2 μm, the second liquid crystal compound 22 is filled in the holes 212 of the honeycomb structure formed by the first liquid crystal compound 21, and the volume ratio of the first liquid crystal compound 21 to the second liquid crystal compound 22 is 0.02 to 0.1: 1. thus, the first liquid crystal compound 21 and the second liquid crystal compound 22 can be fully mixed, and the light scattering property of the liquid crystal layer 2 in an opaque state can be improved; when the first liquid crystal compound 21 and the second liquid crystal compound 22 have the above volume ratio, the main component of the liquid crystal layer 2 is the second liquid crystal compound 22, and the occupation ratio of the second liquid crystal compound 22 is large, so that the effect of an electric field on the liquid crystal layer 2 is very sensitive, and in an actual device, the driving voltage required by the liquid crystal layer 2 is relatively low (e.g., below 10V).

In this embodiment, the first electrode 13 and the second electrode 14 are transparent conductive layers formed by patterning transparent conductive films, and the transparent conductive layers have external terminals extending out of the liquid crystal layer 2. The transparent conductive film can be an ITO film and is patterned through photoetching; the overlap area 15 between the first electrode 13 and the second electrode 14 can be patterned as pixels or segments; the external terminals of the first electrode 13 and the second electrode 14 are used for applying a voltage or a driving signal.

In this embodiment, the first liquid crystal compound 21 and the second liquid crystal compound 22 are nematic liquid crystals having birefringence or compounds thereof; the first liquid crystal compound 21 and the second liquid crystal compound 22 have optical axes corresponding to the liquid crystal molecular orientations thereof, the first liquid crystal compound 21 and the second liquid crystal compound 22 have a first refractive index and a second refractive index respectively in a direction parallel to the optical axes and a direction perpendicular to the optical axes, the first refractive index is greater than the second refractive index, the second refractive index of the second liquid crystal compound 22 is corresponding to the second refractive index of the first liquid crystal compound 21, and the first refractive index of the second liquid crystal compound 22 is corresponding to the first refractive index of the first liquid crystal compound 21. The first and second refractive indexes of the first liquid crystal compound 21 obtained by curing the liquid crystal are easily set to be the same as those of the second liquid crystal compound 22 (the desired refractive index can be easily obtained by a general liquid crystal blending method), the orientations and the optical axes of the first and second

liquid crystal compounds

21 and 22 are also kept to be the same in a natural state, and the back region and the OFF state display region of the liquid crystal display are in a clear and transparent state.

In the present embodiment, the first liquid crystal compound 21 is a positive liquid crystal, a neutral liquid crystal, or a negative liquid crystal; the second liquid crystal compound 22 is a positive liquid crystal whose liquid crystal molecules tend to be parallel to an electric field when subjected to the electric field.

In the present embodiment, the first liquid crystal compound 21 is formed by curing liquid crystal molecules aligned in advance through a cross-linking reaction. The liquid crystal molecules of the first liquid crystal compound 21 may be nematic liquid crystal molecules having an unsaturated group (e.g., -CH = CH2) at an end thereof, and in the manufacturing process, a photosensitizer may be added to the liquid crystal, the liquid crystal is disposed between the first substrate 11 and the second substrate 12 to form the liquid crystal layer 2 (which may be disposed by a common method for liquid crystal displays such as vacuum infusion and drip irrigation), and then ultraviolet light is irradiated to cause a cross-linking reaction of the liquid crystal molecules of the first liquid crystal compound 21 to be cured. Before the first liquid crystal compound 21 is cured, the liquid crystal layer 2 has a certain orientation (e.g., horizontal orientation or vertical orientation, specifically, depending on the material of the inner surfaces of the first substrate 11 and the second substrate 12 (the orientation may be further stabilized by a process such as heating, thermal alignment, etc.), and when the first liquid crystal compound 21 is cured, the orientation is fixed in the first liquid crystal compound 21 (and is not affected by an electric field), and the second liquid crystal compound 22 is affected by the inner surfaces of the first substrate 11 and the second substrate 12 and the first liquid crystal compound 21, and the orientation is kept uniform in a natural state.

In this embodiment, the first and second

liquid crystal compounds

21 and 22 are horizontally aligned; the inner side surfaces of the first substrate 11 and the second substrate 12 are both provided with a horizontal alignment layer 17, and the horizontal alignment layer 17 is a horizontal alignment polyimide coating.

In the PDLC display, since the second liquid crystal compound 22 and the first liquid crystal compound 21 are in intermixed contact with each other, the first liquid crystal compound 21 has an alignment effect on the liquid crystal molecules of the second liquid crystal compound 22, and since the first liquid crystal compound 21 and the second liquid crystal compound 22 have uniform alignment in a natural state (i.e., no voltage is applied to the first electrode 13 and the second electrode 14 and no electric field is present), it can be observed that the OFF state display area is a clear transparent state; since the first liquid crystal compound 21 and the second liquid crystal compound 22 have the same orientation in a natural state, the first liquid crystal compound 21 does not need to seal the second liquid crystal compound 22 into liquid crystal droplets, and the proportion of the second liquid crystal compound 22 can be greatly increased, so that the effect of an electric field on the liquid crystal layer 2 is very sensitive, and in an actual device, the driving voltage required by the liquid crystal layer 2 is relatively low. When a sufficient voltage is applied to the first and

second electrodes

13, 14 to generate an electric field, the orientation of the first liquid crystal compound 21 is unchanged, and the second orientation of each liquid crystal molecule of the second liquid crystal compound 22 deviates from the first orientation with the change of the electric field, so that the second orientation is inconsistent with the first orientation (the liquid crystal molecules in the second liquid crystal compound 22 close to the first liquid crystal compound 21 are deflected relatively little, and the liquid crystal molecules far from the first liquid crystal compound 21 are deflected relatively much), when light passes through the liquid crystal layer 2, it needs to pass through liquid crystal media with different orientations, the refractive indexes of the liquid crystal media with different orientations are generally different ON the propagation path of the light, the light can be scattered or reflected, and an ON state display area can be observed to be in an opaque turbid state. The OFF state display area of the PDLC display is in a transparent state, while the ON state display area is in a turbid state, so that the driving voltage required by the liquid crystal layer 2 can be reduced, the design difficulty of a driving circuit is reduced, and the display mode of white characters ON a black background can be realized under the condition of setting a black background, so that the PDLC display has a wider application range.

In addition, it should be noted that the names of the parts and the like of the embodiments described in the present specification may be different, and the equivalent or simple change of the structure, the characteristics and the principle described in the present patent idea is included in the protection scope of the present patent. Various modifications, additions and substitutions for the specific embodiments described may be made by those skilled in the art without departing from the scope of the utility model as defined in the accompanying claims.

Claims

1. The utility model provides a PDLC display, includes liquid crystal cell and liquid crystal layer, and the liquid crystal cell includes first base plate and the second base plate of mutual bonding, and the liquid crystal layer presss from both sides and establishes between first base plate and second base plate, and the medial surface of first base plate, second base plate is equipped with first electrode, second electrode respectively, and first electrode, second electrode have overlap region, its characterized in that: the liquid crystal layer comprises a first liquid crystal compound and a second liquid crystal compound which are mixed with each other, the first liquid crystal compound is solidified liquid crystal, and liquid crystal molecules of the first liquid crystal compound have fixed first orientation; the second liquid crystal compound is liquid crystal in a fluid state, and liquid crystal molecules of the second liquid crystal compound have a second orientation.

2. The PDLC display of claim 1, wherein: the first liquid crystal compound includes a plurality of segments arranged in an ordered or disordered state and connected to each other, and the second liquid crystal compound is filled in a space other than the first liquid crystal compound.

3. The PDLC display of claim 2, wherein: the multi-section linear bodies are interwoven into a honeycomb structure, the honeycomb structure is provided with a plurality of holes, and the second liquid crystal compound is filled in the holes of the honeycomb structure formed by the first liquid crystal compound.

4. A PDLC display as claimed in claim 3, wherein: the size of the holes is 0.2-2 μm.

5. A PDLC display according to any one of claims 1-4, wherein: the first electrode and the second electrode are transparent conductive layers formed by patterning transparent conductive films, and the transparent conductive layers are provided with external connection ends extending out of the liquid crystal layer.

6. A PDLC display according to any one of claims 1-4, wherein: the first liquid crystal compound and the second liquid crystal compound are nematic liquid crystals with birefringence or compounds thereof; the first liquid crystal compound and the second liquid crystal compound have optical axes consistent with the liquid crystal molecular orientation, and the first liquid crystal compound and the second liquid crystal compound respectively have a first refractive index and a second refractive index in a direction parallel to the optical axes and a direction perpendicular to the optical axes.

7. The PDLC display of claim 6, wherein: the second refractive index of the second liquid crystal compound is consistent with the second refractive index of the first liquid crystal compound.

8. The PDLC display of claim 7, wherein: the first refractive index of the second liquid crystal compound is identical to the first refractive index of the first liquid crystal compound.

9. A PDLC display according to any one of claims 1-4, wherein: the first liquid crystal compound is formed by solidifying liquid crystal molecules which are aligned in advance through a cross-linking reaction; the first liquid crystal compound and the second liquid crystal compound are horizontally oriented, and horizontal orientation layers are arranged on the inner side surfaces of the first substrate and the second substrate.