CN215954025U - PDLC display - Google Patents

Abstract

A PDLC display comprises a liquid crystal box and a liquid crystal layer, wherein the liquid crystal box comprises a first substrate and a second substrate, 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, the first electrode and the second electrode have an overlapping area, and when 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 liquid crystal layer comprises a first liquid crystal compound and a second liquid crystal compound which are mixed with each other, and the first liquid crystal compound is solidified vertical alignment liquid crystal; the second liquid crystal compound is liquid crystal in a fluid state, when no voltage is applied to the liquid crystal layer and no electric field exists, the second liquid crystal compound is prone to horizontal alignment and has alignment difference with the first liquid crystal compound, and when voltage is applied to the first electrode and the second electrode in the overlapping area to generate an electric field, liquid crystal molecules of the second liquid crystal compound tend to be vertically aligned along with the rotation of the electric field to be consistent with the first liquid crystal compound. The PDLC display can reduce the driving voltage required by the liquid crystal layer and reduce the design difficulty of the driving circuit under the condition of keeping the display mode of white-matrix black characters.

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 comprises closed liquid crystal droplets completely encapsulated by a polymer, and the polymer is a transparent photosensitive resin, and in the back area and the OFF-state display pattern (such as a pixel or a pen segment) of the display, when the liquid crystal molecules in the liquid crystal droplets contact with the polymer, the orientation (i.e. the arrangement direction of the liquid crystal molecules) is random, so that the optical axes of the droplets are very disordered, and the liquid crystal layer has a scattering effect on light to make the areas appear a turbid scattering state (such as a milky turbid state); in the ON state display pattern with sufficient voltage applied, the optical axes of the liquid crystal droplets are uniform under the action of the electric field, so that the scattering effect of the liquid crystal layer ON light can be reduced or eliminated, and the liquid crystal layer is in a clear transparent state, and can be in a background color (such as black) under the condition that a background (such as a black background) is padded, so that the display has a white background and black character display mode similar to a printed matter and is favored by consumers. However, the liquid crystal layer of such PDLC display generally uses a large proportion of photosensitive resin to wrap the liquid crystal into closed 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 of the OFF-state display pattern, 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.

SUMMERY OF THE UTILITY MODEL

The utility model provides a PDLC display, which can reduce the driving voltage required by a liquid crystal layer and reduce the design difficulty of a driving circuit under the condition of keeping the display mode of white background black characters. The technical scheme is as follows:

a PDLC display 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, the first electrode and the second electrode have an overlapping area (the overlapping area forms a display pattern of the display, such as a pixel or a pen section), and when voltage is applied to the first electrode and the second electrode, an electric field is formed in the liquid crystal layer of the overlapping area, and the PDLC display is 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, wherein the first liquid crystal compound is solidified vertical orientation liquid crystal (a long molecular axis is vertical to the plane of the first substrate or the second substrate); the second liquid crystal compound is liquid crystal in a fluid state, when no voltage is applied to the liquid crystal layer and no electric field exists (namely, a natural state or an OFF state), the second liquid crystal compound is prone to horizontal orientation (namely, the long axes of molecules are parallel to the plane of the first substrate or the second substrate) and has orientation difference with the first liquid crystal compound, and when the first electrode and the second electrode in the overlapped area are applied with voltage to generate an electric field (namely, an ON state), the liquid crystal molecules of the second liquid crystal compound tend to be vertical orientation along with the rotation of the electric field so as to be consistent with the first liquid crystal compound.

In general, the second liquid crystal compound is a positive liquid crystal whose liquid crystal molecules tend to be parallel to an electric field (i.e., perpendicular to a substrate) when subjected to the electric field.

In the PDLC display, the first and second liquid crystal compounds have different orientations when the liquid crystal layer is in a natural state or an OFF state, and the refractive index of the liquid crystal medium generally changes significantly along the propagation path of light, so that multiple scattering of light may occur when the light passes through the liquid crystal layer, whereby an opaque turbid state may be observed in the background region or the OFF state display pattern. Because 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 in an actual device, the driving voltage required by the liquid crystal layer is lower. When the first and second electrodes of a certain display pattern are applied with sufficient voltage to generate an electric field (i.e., an ON state), the liquid crystal molecules of the second liquid crystal compound tend to be vertically aligned with the rotation of the electric field, the orientations of the first and second liquid crystal compounds tend to be uniform, and in general, the birefringence of the second liquid crystal compound can be made to be uniform with that of the first liquid crystal compound by the preparation of the liquid crystal material, so that the first and second liquid crystal compounds have uniform orientations and birefringence, the change of the refractive index of the liquid crystal medium in the propagation path of light is reduced or eliminated, the scattering of the light is reduced or even eliminated when the light passes through the liquid crystal layer, and the ON state display pattern can be observed to be in a clear and transparent state. The PDLC display has turbid display patterns in the back area and the OFF state, and transparent display patterns in the ON 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 white background black character display mode of the PDLC display can be maintained.

Generally, the first and second substrates 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 a seal for the liquid crystal layer; and a spacer (such as spacer balls) for maintaining the thickness of the liquid crystal layer (generally 3-10 μm) is arranged between the first and second substrates.

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 preferable 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 and second liquid crystal compounds have the above volume ratio, the main component of the liquid crystal layer is the second liquid crystal compound, and the second liquid crystal compound has a large occupation ratio, so that the electric field is very sensitive to the liquid crystal layer, and in an actual device, the driving voltage required by the liquid crystal layer is lower (e.g., below 10V).

In a preferred embodiment, the first and second electrodes 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 and second electrodes can be made into the pattern of pixels or pen segments; the external terminals of the first and second electrodes are used for applying voltage or driving signals.

In a preferred embodiment, the first liquid crystal compound is cured by a cross-linking reaction of liquid crystal molecules, and the liquid crystal molecules gradually form a vertical orientation during the cross-linking reaction. The liquid crystal molecules of the first liquid crystal compound may be modified to include a side chain modified with a non-saturated group (e.g., -CH = CH)₂) The liquid crystal molecules of (1) can be cured by adding photosensitizer into liquid crystal, disposing the liquid crystal between the first substrate and the second substrate to form a liquid crystal layer (which can be disposed by common liquid crystal display methods such as vacuum infusion and drip irrigation), and irradiating with ultraviolet light to crosslink the liquid crystal molecules of the first liquid crystal compound, wherein the liquid crystal molecules are crosslinked with side chains to form a crosslinked liquid crystal compoundThe liquid crystal molecules in the rows are horizontally arranged by the horizontal anchoring action of the inner surfaces of the first and second substrates, so that the liquid crystal molecules (monomers) in the liquid crystal molecules are converted into vertical orientation, and the first liquid crystal compound is cured along with the deepening of the cross-linking reaction of the liquid crystal molecules, and the vertical orientation of the first liquid crystal compound is finally fixed.

The second liquid crystal compound is generally horizontally oriented by the inner surfaces of the first and second substrates. In a preferred embodiment, 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 horizontal orientation layer can also be further provided with an orientation effect of a determined angle through an orientation friction process.

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 vertical orientation liquid crystal; the second liquid crystal compound is liquid crystal in a fluid state, and liquid crystal molecules of the second liquid crystal compound are horizontally oriented in a natural state or an OFF state; the first liquid crystal compound is not uniformly oriented in a natural state or an OFF state, so that the background area of the display and the display pattern are in a turbid scattering state; because 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 the first and second electrodes of a certain display pattern are applied with sufficient voltage to generate an electric field, the orientation of the first liquid crystal compound is not changed, and the orientation of the liquid crystal molecules of the second liquid crystal compound tends to be vertical orientation along with the rotation of the electric field so as to be consistent with that of the first liquid crystal compound, so that the display pattern in an ON state is in a clear transparent state. The PDLC display can reduce the driving voltage required by the liquid crystal layer, reduce the design difficulty of the driving circuit and keep the display mode of black characters on white background.

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 reaction scheme of liquid crystal molecules of the first liquid crystal compound of the PDLC display and curing thereof according to the preferred embodiment of the present invention.

FIG. 4 is a schematic view of the liquid crystal molecules of FIG. 3 anchored in rows on an alignment layer after curing.

Fig. 5 is a schematic diagram of the liquid crystal orientation and its light contribution of the OFF state display pattern in the PDLC display of fig. 1, wherein the horizontal and vertical lines represent horizontal and vertical orientations, respectively.

Fig. 6 is a schematic diagram of the liquid crystal orientation and its light contribution of the ON state display pattern in the PDLC display of fig. 1, wherein the horizontal and vertical lines represent horizontal and vertical orientations, respectively.

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, the first electrode 13 and the second electrode 14 have an overlapping region 15, the overlapping region 15 forms a display pattern (such as a pen segment or a pixel) of the display, 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; when no voltage is applied to the first and second electrodes 13 and 14, the second and first orientations are horizontal and vertical orientations, respectively, and when a voltage is applied to the first and second electrodes 13 and 14, which generates an electric field, the second orientation is aligned with the first orientation as the electric field changes to the vertical orientation.

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 formed by curing the liquid crystal are easily set to be consistent with those of the second liquid crystal compound 22 (the required refractive index can be easily obtained by a common liquid crystal blending method), and in the ON state, the orientations and the optical axes of the first and second liquid crystal compounds 21 and 22 tend to be consistent, and the display pattern of the ON state of the liquid crystal display is in a clear transparent state.

In the present embodiment, 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 the liquid crystal molecules 211 aligned in advance through a crosslinking reaction. The liquid crystal molecules 211 of the first liquid crystal compound 21 may include a side chain modified with a non-saturated group (e.g., -CH = CH)₂) In the manufacturing process, a photosensitizer is added into the liquid crystal, the liquid crystal is arranged between the first substrate 11 and the second substrate 12 to form a liquid crystal layer 2 (which can be arranged by common liquid crystal display common methods such as vacuum infusion, drip irrigation and the like), ultraviolet light is irradiated to cause the liquid crystal molecules of the first liquid crystal compound 21 to generate a cross-linking reaction and be cured, in the cross-linking reaction process, the liquid crystal molecules are mutually cross-linked by side chains to form rows, and the rows of liquid crystal molecules are horizontally arranged under the horizontal anchoring action of the inner surfaces of the first substrate and the second substrate, so that the liquid crystal molecules (monomers) in the rows are converted into vertical orientation, and the vertical orientation of the liquid crystal molecules is finally fixed along with the deepening of the cross-linking reaction of the liquid crystal molecules.

In this embodiment, the inner side surfaces of the first substrate 11 and the second substrate 12 are both provided with the horizontal alignment layer 17, and the horizontal alignment layer 17 is a horizontal alignment polyimide coating. The second liquid crystal compound 22 is horizontally oriented in a natural state by the inner surfaces of the first substrate 11 and the second substrate 12.

In the PDLC display, since the first and second liquid crystal compounds 21 and 22 have non-uniform orientations in the natural state or the OFF state, the background region and the OFF state display pattern are observed to be in a turbid scattering state; since the first liquid crystal compound 21 does not need to seal the second liquid crystal compound 22 into liquid crystal droplets, the ratio of the second liquid crystal compound 22 can be greatly increased, so that the effect of the 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 and 14 to generate an electric field, the liquid crystal molecules of the second liquid crystal compound 22 tend to align with the first liquid crystal compound as the electric field rotates, and when light passes through the liquid crystal layer 2, the refractive indexes of different liquid crystal media are nearly identical, so that the scattering or reflection of light is reduced, and thus the ON state display pattern is observed to be in a clear transparent state. The PDLC display has turbid background areas and OFF state display patterns and transparent ON state display patterns, 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 black characters ON white background can be maintained.

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 (9)

1. A PDLC display 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, the first electrode and the second electrode have an overlapping area, and when voltages are applied to the first electrode and the second electrode, an electric field is formed in the liquid crystal layer of the overlapping area, and the PDLC display is 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, and the first liquid crystal compound is solidified vertical alignment liquid crystal; the second liquid crystal compound is liquid crystal in a fluid state, when no voltage is applied to the liquid crystal layer and no electric field exists, the second liquid crystal compound is prone to be horizontally aligned and has an alignment difference with the first liquid crystal compound, and when the first electrode and the second electrode in the overlapped area are applied with voltage to generate an electric field, liquid crystal molecules of the second liquid crystal compound tend to be vertically aligned along with the rotation of the electric field so as to be consistent with the first liquid crystal compound.

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 1, 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. The PDLC display of claim 1, wherein: the size of the holes is 0.2-2 μm.

5. The PDLC display of claim 1, wherein: the volume ratio of the first liquid crystal compound to the second liquid crystal compound is 0.02-0.1: 1.

6. the PDLC display of claim 1, wherein: the first liquid crystal compound is cured by liquid crystal molecules through a cross-linking reaction, and the liquid crystal molecules gradually form vertical orientation in the process of the cross-linking reaction.

7. The PDLC display of claim 1, wherein: the first liquid crystal compound is formed by the cross-linking reaction of liquid crystal molecules which comprise side chains and are modified with unsaturated groups.

8. The PDLC display of claim 7, wherein: in the process of the cross-linking reaction, the liquid crystal molecules are firstly cross-linked with each other by side chains to form a row, the liquid crystal molecules in the row are horizontally arranged under the horizontal anchoring action of the inner surfaces of the first substrate and the second substrate, so that the liquid crystal molecules in the row are converted into vertical orientation, the first liquid crystal compound is cured along with the deepening of the cross-linking reaction of the liquid crystal molecules, and the vertical orientation is finally fixed.

9. The PDLC display of claim 1, wherein: and the inner side surfaces of the first substrate and the second substrate are provided with horizontal orientation layers.

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