Patent Grant
9175220
This application is a United States National Stage application filed under 35 U.S.C. §371 of PCT Patent Application Serial No. PCT/CN2011/085036 filed on Dec. 30, 2011 which claims benefit of and priority to Chinese Patent Application Serial No. 201110451207.7 filed Dec. 29, 2011, the disclosures of all of which are hereby incorporated by reference in their entirety.
The present invention relates to a high scattering smectic liquid crystal material and displays using the same, which belong to the technical field of optical display materials and display devices.
The study on using smectic liquid crystal as display material has a history of over 30 years. Monitors using the smectic liquid crystals as the display materials are reflective display devices, which have no polarizer plate and backlight, compared with common liquid crystal display devices. Such monitors rely mainly on reflection of external light, resulting in lower contrast and making commercialization more difficult.
The study on the smectic liquid crystal material is focused on ferroelectric liquid crystal and antiferroelectric liquid crystal that belong to smectic A phase and smectic C phase. The ferroelectric liquid crystal and antiferroelectric liquid crystal materials are used in surface stabilized display devices. Since uniform, perfect and regular arrangement is required for both the liquid crystal molecules and the liquid crystal layers in this kind of devices, and the thickness of a liquid crystal cell is required to be 1 to 2 μm, the manufacturing process of such devices is very difficult, and large scale production cannot be achieved, so the ferroelectric liquid crystal devices have not enter a practical commercial application stage.
There are few smectic liquid crystal materials. WO 2010/070606 A1 discloses a method for obtaining a wide-temperature range smectic phase. Actual tests show that the contrast of this material is undesirable, making it infeasible to be used in actual display devices.
Therefore, in the field of display application of multi-stable liquid crystals, there is an urgent need for a high scattering smectic liquid crystal material that can be used in display devices having an excellent optical structure, so as to increase the contrast of the smectic crystal display devices and achieve a good display effect.
The present invention is directed to a series of smectic liquid crystal mixed materials having high scattering, and the smectic liquid crystal mixed materials having high scattering are successfully applied to display devices having an excellent optical structure, in combination with a drive method suitable for the display material, thereby obtaining a smectic multi-stable liquid crystal display device that is available for commercial applications, has a high contrast and a good display quality, and is energy saving.
In the present invention, a series of smectic A phase liquid crystals having compact arrangement of crystal domains or a series of smectic liquid crystal mixed materials having a degree of order higher than that of the smectic phase A and an optical texture different from that of the smectic A phase, for example, the smectic B, H and G, are obtained by mixing smectic liquid crystal compounds of different types or mixing a smectic liquid crystal compound with an organic compound having a high optical anisotropy (Δn). When being applied in a smectic stable state liquid crystal display mode, this type of materials have a high scattering state, so the contrast of the smectic liquid crystal display devices can be effectively improved. When the present invention is applied to a reflective smectic liquid crystal display device, a smectic display device having a high contrast is obtained.
In the present invention, a mixed liquid crystal having high scattering is prepared. The high scattering smectic liquid crystal material of the present invention is a mixed liquid crystal material, comprising two or more compound represented by Formula (I).
In Formula (I), R1 is C1-C20 alkyl, C1-C20 alkoxy, C1-C20 alkenyl, C1-C20 alkenyloxy, silanyl, siloxanyl and halogenated groups thereof; and C1-C20 alkyl, C1-C20 alkoxy, C1-C20 alkenyl, C1-C20 alkenyloxy, silanyl and siloxanyl and isomers thereof with any —CH2— substituted with —O—, —S—, —CF2—, —CF2O—, —CO—, —COO—, —O—CO—, —O—COO—, —CF═CF—, —CH═CF—, —CF═CH— or —CH═CH—;
Preferably, R1 is selected from the group consisting of: C1-C15 alkyl, C1-C15 alkoxy, C1-C15 alkenyl, C1-C15 alkenyloxy, C1-C15 silanyl, C1-C15 siloxanyl and halogenated groups thereof; and C1-C15 alkyl, C1-C15 alkoxy, C1-C15 alkenyl, C1-C15 alkenyloxy, C1-C15 silanyl and C1-C15 siloxanyl and isomers thereof with any —CH2— substituted with —O— or —S—.
More preferably, R1 is selected from the group consisting of: C1-C10 alkyl, C1-C10 alkoxy, C1-C10 alkenyl, C1-C10 silanyl, C1-C10 siloxanyl and halogenated groups thereof; and C1-C10 alkyl, C1-C10 alkoxy, C1-C10 alkenyl, C1-C10 silanyl and C1-C10 siloxanyl and isomers thereof with any —CH2— substituted with —O—.
R2 is CN, F, NCS, NCO, CF3, CHF2, CH2F, OCF3, OCHF2, OCH2F, NO2, Cl, CH═CF2 and OCH═CF2; C1-C20 alkyl, C1-C20 alkoxy, C1-C20 alkenyl, C1-C20 alkenyloxy, C1-C20 silanyl and C1-C20 siloxanyl, and halogenated groups thereof; and C1-C20 alkyl, C1-C20 alkoxy, C1-C20 alkenyl and C1-C20 alkenyloxy and isomers thereof with any —CH2— substituted with —O—, —S—, —CF2—, —CF2O—, —CO—, —COO—, —O—CO—, —O—COO—, —CF═CF—, —CH═CF—, —CF═CH— or —CH═CH—.
Preferably, R2 is selected from the group consisting of: CN, F, NCS, CF3, CHF2, CH2F, OCF3, OCHF2, OCH2F, and Cl; C1-C15 alkyl, C1-C15 alkoxy, C1-C15 alkenyl, C1-C15 alkenyloxy, C1-C15 silanyl, C1-C15 siloxanyl and halogenated groups thereof; and C1-C15 alkyl, C1-C15 alkoxy, C1-C15 alkenyl and C1-C15 alkenyloxy and isomers thereof with any —CH2— substituted with —O— or —S—.
More preferably, R2 is CN, F, NCS, CF3 or OCF3.
A, B, C and D each has a rigid ring structure and each independently comprises:
or cycloalkenyl; wherein the hydrogen atoms X1 to X14 on the ring structures are either unsubstituted or indendently substituted with CN, F, CF3, CHF2, CH2F, OCF3, OCHF2, OCH2F, NO2, Cl, alkyl or alkoxy.
Preferably, A, B, C and D are independently selected from the group consisting of:
More preferably, A, B, C and D are independently selected from the group consisting of:
Z1 to Z3 are independently: a single bond (that is, two rigid moieties are directly connected), C1-C20 alkyl, C1-C20 alkoxy, C1-C20 alkenyl, C1-C20 alkenyloxy, C1-C20 silanyl and C1-C20 siloxanyl; and C1-C20 alkyl, C1-C20 alkoxy, C1-C20 alkenyl, C1-C20 alkenyloxy, C1-C20 silanyl and C1-C20 siloxanyl and isomers thereof with any —CH2— substituted with —O—, —S—, —CO—, —COO—, —O—CO—, —O—COO—, —CF═CF—, —CHF—, —CF2—, —CF2O—, —CH2O—, —OCH2—, —CH═CH—, —CH═N—, —C≡C—, —CH═N—N═CH—, —CH═CF—, —CF═CH—, —CH2CF2—, —CF2CH2— or
Preferably, Z1 to Z3 are independently selected from the group consisting of: a single bond, —C2H4—, —CH═CH—, —C≡C—, —CF2O—, —CH2O—, —COO— and —CH═N—N═CH—.
More preferably, Z1 to Z3 are independently selected from the group consisting of: a single bond, —C2H4—, —CH═CH—, —C≡C—, —CF2O—, —CH2O— and —COO—.
X1 to X14 are independently selected from the group consisting of: H, CN, NCS, F, Cl, CF3, CHF2, CH2F, OCF3, OCHF2, OCH2F, NO2, alkyl and alkoxy.
Preferably, X1 to X14 are independently selected from the group consisting of: H, CN, NCS, F, C1 and CF3.
More preferably, X1 to X14 are independently selected from the group consisting of: H, CN, F and Cl.
M1, M2, M3 and M4 are independently 0, 1 or 2, and M1+M2+M3+M4≧2. Preferably, M1, M2, M3 and M4 are independently 0 or 1, and M1+M2+M3+M4≧2.
When being used as a display material, any compound alone cannot satisfy all requirements, so a variety of compounds having excellent photoelectric properties are selected and mixed at a certain ratio to form a mixed liquid crystal for the purpose of satisfying various performance requirements. Similarly, in order to further improve the degree of scattering of the smectic liquid crystal material on a basis of ensuring the other excellent properties, selection of the compounds and the formulation ratio thereof need to be optimized. Therefore, in the present invention, mixing of different compounds is studied and a high scattering mixed smectic liquid crystal material that can improve the contrast is provided.
In the present invention, a mixed liquid crystal having high scattering is prepared. In addition to two or more organic compound represented by Formula (I), the high scattering smectic liquid crystal material of the present invention may further comprise one or more ionic compound represented by Formula (II).
R3—X+Y− Formula (II)
In Formula (II), R3 is: C0-C20 alkyl, C0-C20 alkoxy, C0-C20 alkenyl and C0-C20 alkenyloxy, and halogenated groups thereof; ferrocenylmethyl and phenyl; and C0-C20 alkyl, C0-C20 alkoxy, C0-C20 alkenyl, C0-C20 alkenyloxy and isomers thereof with any —CH2— substituted with —O—, —S—, —CF2—, —CF2O—, —CO—, —COO—, —O—CO—, —O—COO—, —CF═CF—, —CH═CF—, —CF═CH—, —CH═CH—,
or phenyl.
Preferably, R3 is selected from the group consisting of: C0-C16 alkyl, C0-C16 alkoxy, C0-C16 alkenyl, C0-C16 alkenyloxy, ferrocenylmethyl and phenyl; and C0-C16 alkyl, C0-C16 alkoxy, C0-C16 alkenyl and C0-C16 alkenyloxy and isomer thereof with any —CH2— substituted with —O—, —S—,
and phenyl.
More preferably, R3 is selected from the group consisting of: C0-C16 alkyl, phenyl; and C0-C16 alkyl and isomers thereof with any —CH2— substituted with
and phenyl.
X+ is a cation selected from the group consisting of: Na+, K+, N+, [(R4)3]N+, [(R4)3]P+,
wherein R4 is C1-C30 alkyl, C1-C30 alkoxy, C1-C30 alkenyl, C1-C30 alkenyloxy or halogenated groups thereof, or phenyl, and R5 is C1-C30 alkyl, C1-C30 alkoxy, C1-C30 alkenyl, C1-C30 alkenyloxy, or halogenated groups thereof, or phenyl.
Preferably, X+ is a cation selected from the group consisting of: Na+, K+, N+, [(R4)3]N+, [(R4)3]P+,
wherein R4 is C1-C20 alkyl, C1-C20 alkoxy, C1-C20 alkenyl, C1-C20 alkenyloxy, or halogenated groups thereof, or phenyl; and R5 is C1-C20 alkyl, C1-C20 alkoxy, C1-C20 alkenyl, C1-C20 alkenyloxy, or halogenated groups thereof, and phenyl.
More preferably, X+ is a cation selected from the group consisting of: Na+, K+, N+, [(R4)3]N+, [(R4)3]P+,
wherein R4 is C1-C16 alkyl or phenyl; and R5 is C1-C16 alkyl or phenyl.
Y− is an anion selected from the group consisting of: F−, Cl−, Br−, I−, (PF6)−, (Ph4B)−, SO4−, ClO4− and
Preferably, Y− is an anion selected from the group consisting of: F−, Cl−, Br−, (PF6)−, (Ph4B)−, SO4−, ClO4−; and
More preferably, Y− is an anion selected from the group consisting of: F−, Cl−, Br−, (PF6)−, (Ph4B)−, SO4− and ClO4−.
Most preferably, the ionic compound represented by Formula (II) has a structure represented by Formula (VII),
wherein R is selected from the group consisting of: C0-C16 alkyl and C0-C16 terminal alkenyl; and
X− is an anion selected from the group consisting of: F−, Cl−, Br−, (PF6)−, (Ph4B)−, SO4− and ClO4−.
In the present invention, a series of mixed liquid crystals having compact arrangement of crystal domains are obtained with the novel high scattering smectic liquid crystal material through mixing, so that the light entering the mixed liquid crystals exhibit a higher scattering state. The high scattering smectic liquid crystal material of the present invention may be a smectic A phase or a non-smectic A phase liquid crystal material, where the non-smectic A phase liquid crystal material may be a smectic B, C, D, E, F, G, H, or I phase material, or a undefined smectic X phase materials having a degree of order higher than that of the smectic A phase. The mixed material may be used in existing smectic liquid crystal display devices, and the contrast of the existing display devices can be effectively improved.
The high scattering smectic liquid crystal material of the present invention preferably contains a smectic liquid crystal compound and at least one of a compound A, a compound B and a compound C.
In the present invention, the following aspects are studied.
1) Long-Carbon Chain Smectic Materials
50 wt % cyanobiphenyl compounds having different carbon chain lengths are mixed with 50 wt % I102 and 10OCB, where I102:10OCB=4:1 (weight ratio). After mixing, 4 wt ‰ cetyltrimethyl ammonium perchlorate is added, to prepare a liquid crystal mixed layer; and then, the transmittance at clearing state, the transmittance at frosting state and the contrast are tested, with the results shown in Table 1.
Linear cyanobiphenyl compounds are a very important class of compounds, and are the smectic A phase materials when the number of carbon in the chain section is higher than 8. It can be seen that, long carbon chain is favorable for the formation of the smectic phase, so it is supposed that the contrast may be improved by extending the carbon chain. Therefore, the linear cyanobiphenyl compounds having different carbon chain lengths are compared (data is shown in Table 1); however, it is found that 8CB with the shortest chain has the best effect.
the figure before CB represents the number of carbon atoms in the carbon chain
2) Reduction of Amount of Siloxane Liquid Crystals
Different amounts of I102 are mixed with 10OCB, 8CB and B1, where 10OCB:8CB:B1=1:2:1 (weight ratio). After mixing, 4 wt ‰ cetyltrimethyl ammonium perchlorate is added, to prepare a liquid crystal mixed layer; and then, the transmittance at clearing state, the transmittance at frosting state and the contrast are tested, with the results shown in Table 2.
The structure of the siloxane liquid crystal molecule contains a flexible and large siloxanyl group, the flexible long chain section of the siloxane liquid crystal molecule is long, the ratio of the volume of the flexible moiety in the whole molecular size is large, and generally, the interstice caused by arrangement of the flexible moiety in the smectic layer is higher than that caused by the rigid moiety, so the “interstices” in the smectic layer formed in siloxane liquid crystal are more, and the probability of the light passing through these “interstices” is large at frosting state. Therefore, the transmittance at frosting state is large, and the contrast is low. In theory, the contrast may be improved by reducing the content of the siloxane liquid crystal in the formulation. A series of experiments show that when the amount of siloxane liquid crystals is lower than 10%, the contrast can be up to 5:1.
3) Addition of Compounds Having a Large Optical Anisotropy (Δn) for Mixing
the contrast of the liquid crystal material is significantly correlated with the optical anisotropy (Δn) of the liquid crystal material, and in general, the liquid crystal material having a high optical anisotropy (Δn) has a high contrast, so it is tried to adding a liquid crystal material having a high optical anisotropy (Δn) for mixing.
A) Addition of Alkyne Liquid Crystals
In the nematic phase formulation, in order to improve the contrast of the liquid crystal, an alkyne liquid crystal material having a high optical anisotropy (Δn) is often added. It is found that addition of the alkyne liquid crystal can improve the contrast of the smectic liquid crystal formulation; however, it is found through repeated experiments that the change of the contrast of the smectic phase formulation varies with the amount of the alkyne liquid crystal material, that is, at the beginning, the contrast of the smectic phase formulations gradually increases with the increase of the amount of the alkyne liquid crystal material, and after the contrast reaches 7.5:1, the contrast maintains constant and then gradually drops with the increase of the amount of the alkyne liquid crystal material, with the specific date shown in Table 3.
The method for improving the contrast by adding an alkyne liquid crystal is not limited to the materials having the structures above, and addition of the alkyne liquid crystal materials having a structure other than the structures of Formulas above can also improve the contrast.
B) Addition of Cyanoterphenyl Liquid Crystals
5CT (n-pentyl cyanoterphenyl) materials are a type of materials that are commercially available and have a high optical anisotropy (Δn), and are used in some experiments. It is found that when the content of 5CT is higher than 20 wt %, it is difficult to dissolve, and when the content is increased to 10%, the limit of the contrast is reached, and further addition had no contribution to the contrast, with the data shown in Table 4.
C) Addition of Polycyclic Materials
In general, the larger the conjugated moiety in the liquid crystal material, the higher the optical anisotropy (Δn), where the conjugated moiety in the material generally depends on the rigid moiety, and the rigid moiety generally formed by multiple rigid rings through connection. By comparison of multiple polycyclic materials, a polyphenyl material having an excellent performance is found, which has a contrast of up to 8:1, with data shown in table 5.
D) Addition of Heterocyclic Liquid Crystals for Mixing
A heterocyclic liquid crystal generally has an optical anisotropy (Δn) higher than that of a liquid crystal having a similar structure. In the experiments of mixing smectic liquid crystals, it is found that when the liquid crystal monomer in the formulation is replaced by a heterocyclic liquid crystal having a similar structure, the contrast is significantly improved, with the specific experimental data shown in Table 6. It is found by analyses that, due to addition of some heterocyclic liquid crystals, small crystal domains in the focal conic texture of the smectic A phase become much larger, and it is found that the size of the crystal domains is 5 to 10 times larger than the size of the crystal domains of the common smectic A phase formulations through observation with a polarizing microscope.
The methods for expanding the smectic A phase crystal domains or obtaining the non-smectic A phase textures by adding heterocyclic liquid crystals are not limited to addition of the materials having the above structures, and addition of heterocyclic liquid crystal materials having a structure other than the structures represented by the structural formulas above can also improve the contrast.
It is found through the tests above, the contrast can be improved by adding one or more of four materials below to the common smectic A, B, C, D, E, F, G, H or I phase liquid crystal materials, such as the smectic A phase materials (I102, 8CB).
a. Alkyne Liquid Crystals
where R6 is C1-C10 alkyl or C1-C10 alkoxy;
R7 is CN, NCS or F.
E and F are independently selected from the group consisting of:
X15 to X20 are independently selected from the group consisting of: H and F.
M5 and M6 may independently be 0 or 1.
b. Heterocyclic Rings
where R8 is C1-C10 alkyl or C1-C10 alkoxy;
R9 is CN, NCS or F.
G and H are independently selected from the group consisting of:
X21 to X22 are independently selected from the group consisting of: H and F.
M7 and M8 may independently be 0 or 1, and M7+M8≧1.
c. Difluoro Ethers
where R10 is C1-C10 alkyl or C1-C10 alkoxy;
R11 is CN, NCS or F.
The ring structure I is selected from the group consisting of:
X23 to X28 are independently selected from the group consisting of: H and F.
M9 may independently be 0 or 1.
d. Polycyclic Biphenyls
where R12 is C1-C10 alkyl or C1-C10 alkoxy;
R13 is CN, NCS or F.
The ring structure J and K are selected from the group consisting of:
Z4 is selected from the group consisting of: a single bond, —COO—, —C2H4— and
X29 to X32 are independently selected from the group consisting of: H and F.
M10 and M11 may independently be 0 or 1.
4) Addition of Other Smectic Phases for Mixing
According to the molecular arrangement and texture, the smectic liquid crystals are classified into different phases, namely, the smectic A, B, C, D, E, F, G, H and I, where the smectic A phase has the lowest degree of order. It is found through a large number of experiments that when being mixed with the other smectic liquid crystals, the crystal domains of the smectic A phase are significantly expanded, and the contrast is improved; and in some cases, a smectic phase having a optical texture other than the smectic A phase may be obtained, and once the mischcrystal is changed into a non-smectic A phase, the contrast is significantly improved. The reason is that the liquid crystals with the other smectic phases have a relatively high degree of order, and the degree of order of the mischcrystal is increased by mixing with other materials. The basic method includes mixing the compounds of Formula (I) with the smectic B, C, D, E, F, G, H or I phase liquid crystal materials independently, and the smectic A, B, C, D, E, F, G, H and I phase mischcrystal materials, even some undefined new mischcrystal materials can be obtained by adjusting the ratio.
In addition, a mixture having a degree of order higher than that of the smectic A phase can be obtained by mixing the non-smectic A phase smectic liquid crystal material with some compounds having a length-diameter ratio, thereby achieving the purpose of improving the contrast.
In the present invention, the contrast of the smectic display devices is improved by modifying the optical texture of the common smectic A phase. The specific technical means include, but not limited to, mixing with the heterocyclic liquid crystals, and mixing with different smectic materials. The high scattering smectic liquid crystal material obtained in the present invention is a smectic A phase material or a mischcrystal material of the smectic B, C, D, E, F, G, H or I phase having a degree of order higher than that of the smectic A phase.
In the smectic liquid crystal display device, the high scattering smectic liquid crystal material of the present invention may be combined with a spacer, in some cases also with a polymer, to form a mixed liquid crystal layer of a smectic liquid crystal display. In the mixed liquid crystal layer formed by the high scattering smectic liquid crystal material of the present invention, the content of compound represented by Formula (I) is 1 wt % to 100 wt %, preferably 10 wt % to 100 wt %, based on the total weight of the mixed liquid crystal layer; the content of the ionic compounds, preferably such as cetyltrimethyl ammonium perchlorate, is 0.0001 wt % to 10 wt %, preferably 0.0001 wt % to 1 wt %, based on the total weight of the mixed liquid crystal layer.
The drive display principle of the smectic phase liquid crystal applied to display is shown in
In a low frequency electric field (≦100 Hz), long-chain conductive ions (the conductive material, such as added organic conductive ions, such as tetrabutylammonium bromide, sodium laurylsulfate, cetyltrimethyl ammonium perchlorate, and tetraphenylphosphonium iodide) begin to move back and forth under the electric field force, thereby agitating and disturbing the smectic layer in ordered arrangement. This behavior is similar to the dynamic scattering effect of the nematic liquid crystal, and difference lies in that, the vortex plane formed during the smectic dynamic scattering is perpendicular to the direction of the applied electric field, while the vortex plane formed during the dynamic scattering of the nematic liquid crystals is parallel to the direction of the applied electric field. The molecular arrangement of the smectic liquid crystal is kept in a disordered state as shown in the lower left panel of
In high-frequency electric field (≧1000 Hz), the organic conductive ions move back and forth slightly, and the agitation effect on the liquid crystal is negligible. Herein, under the electric field force, the major axis of the liquid crystal molecules are oriented in parallel to the direction of the electric field; when the electric signal is stopped, this regular arrangement is maintained, as shown in the right side in the figure below. At this time, when observing the liquid crystal cell by using the transmittance light from a microscope, it can be viewed that the electrode region is in a bright state that light can transmit, resulting in a clearing state.
The molecular arrangement of the smectic liquid crystal can also remain in various states where the light transmittance is different, so as to achieve display at different grey levels. Therefore, the smectic liquid crystal may have the feature of multi-stable states.
The high scattering smectic material of the present invention can also be filled between two plastic films or two pieces of glass with a conductive layer and serving as a dimming medium, and can also be filled in vacuum into a lattice screen to serve as a display device.
In order to control the thickness of the liquid crystal cell, in the high scattering smectic material of the present invention, a spacer ball, a spacer rod made of polyester or polystyrene, or a glass material may be added; in order to reduce the working viscosity and improve the bonding firmness of the liquid crystal cell, a prepolymer may be added in the high scattering smectic material; and in order to achieve the effect of color display, a dichroic dye may be added in the high scattering smectic material.
The high scattering smectic material of the present invention is not limited to be used as a material in the dimming medium or a display device, and can be used in all the devices with a dual-frequency drive mode of low-frequency frosting and high-frequency clearing.
1. In the present invention, a new method for mixing the smectic liquid crystal material is used to obtain a series of smectic A phase liquid crystals having compact arrangement of crystal domains or a series of smectic liquid crystal mixed materials having a degree of order higher than that of the smectic A phase and an optical texture different from that of the smectic A phase, for example, the smectic B, H and G, and when being applied in a multi-stable smectic liquid crystal display pattern, this type of materials have a high scattering state.
2. When being applied to an existing smectic liquid crystal display, the mixed material of the present invention can effectively improve the contrast of the existing display. The contrast acceptable for human eyes is generally 5:1, and the high scattering smectic material provided by the present invention have a contrast of 6:1 to 12:1 without any optical processing aids, thereby providing good visual effects.
The present invention is further described below with reference to the accompanying drawings and specific embodiment, which are not intended to limit the scope of the present invention.
In the present invention, mixing and tests are performed following the following liquid crystal mixing experimental procedure:
1. selected materials are weighed at a specified ratio, and are added one by one into a glass vial;
2. the vial containing the materials is placed in an oven and heated until the liquid crystal is completely clear;
3. the liquid crystal is fully and uniformly mixed through ultrasonic shock or magnetic stirring;
4. the mixed liquid crystal is heated and filled into a liquid crystal cell having a thickness of 12 micrometers;
5. at a voltage of ±40 V, frosting is performed on the liquid crystal cell at a frequency of 30 Hz and clearing is performed at a frequency of 2 KHz, with all waves in the form of square waves; and
6. the liquid crystal cell was tested for the contrast.
The contrast of the smectic liquid crystal display is a ratio of the light transmittance at the clearing state to the light transmittance at the frosting state for the device, and in general, all materials have substantially the same light transmittance at the clearing state; therefore, the contrast mainly depends on the light transmittance of the material at the frosting state, that is, the scattering state of the smectic liquid crystal material.
Since no standard method for testing the contrast of the reflective smectic liquid crystal display device is available in the industry, multiple universal and simple methods are used to test the contrast, and finally, a test method having a visual effect closer to that of human eye is selected and used as the standard of verification and comparison.
Contrast Test Method: Microscopy Method
This test method is a simple method that is often used for testing and has measurement results close to human eyes, and the apparatus used by the method is shown in
Test Procedure:
1. A sample is placed on an objective table, and the focal length of the microscope is adjusted, so that the sample can be imaged clearly.
2. The sample was removed, and the HL-CR-11A software was used to compute with the numerical values at each points collected by CCD as follows:
Yi=0.299*R+0.587*G+0.114*B.
3. The Yi values at each points are summed to give a normalized factor Y0=ΣYi.
4. The sample is placed onto the objective table, and the HL-CR-11A software is used to compute the Y value at this point Y=ΣYi.
5. The transmittance of the sample is defined as T=(Y/Y0)*100%.
6. For the smectic liquid crystal sample, the transmittance at clearing state Tc=(Yc/Y0)*100%, the transmittance at frosting state Ts=(Ys/Y0)*100%, and the contrast Cr═Tc/Ts.
In brief, first, in the situation that no liquid crystal cell is placed on the objective table and a light source (light ray emitted from a halide lamp equipped on the microscope) directly enter the objective lens, the light rays are collected by a receiver, the receiver converts the collected light rays into corresponding electric signals and send the electric signals to software of a computer, and the software records an electric signal B at this point as a basic reference value. Next, the luminance L of the light source at this point is fixed, the liquid crystal cell is placed on an objective table and the height of the objective table is adjusted, so that the liquid crystal cell can be clearly observed from an ocular lens; the receiver converts the light ray energy collected from the liquid crystal cells at the clearing state and the frosting state into an electric signal and sent the electrical signal to the computer. The computer software compares the light ray energy received at the clearing state and the frosting state with the basic reference. That is, the electric signal Q of the light ray energy received at the clearing state is divided by the basic reference value B to obtain a transmittance value QL at the clearing state, the electric signal M of the light ray energy received at the frosting state is divided by the basic reference value B to obtain a transmittance value ML at the frosting state, and the transmittance at the clearing state is divided by the transmittance at the frosting state to obtain a contrast value QL/ML*100%.
The view of the texture of the mischcrystal in this embodiment is shown in
According to the mixing method and the contrast test method in Embodiment 1, experiments are performed on the formulation in Table 8, and the following embodiment are the same.
As shown in
The texture is observed by using a microscope, and the liquid crystal is the smectic B liquid crystal, has compact arrangement of crystal domains, and has a good shading effect at the frosting state. The transmittance is tested as 90% at clearing state and is merely 9% at the frosting state, and the contrast is 10:1.
The texture is observed by using a microscope, and the liquid crystal is the smectic C liquid crystal, has compact arrangement of crystal domains, and has a good shading effect at the frosting state. The transmittance is tested as 90% at the clearing state and is merely 10% at the frosting state, and the contrast is 9:1.
The texture is observed by using a microscope, and the liquid crystal is the smectic D liquid crystal, has compact arrangement of crystal domains, and has a good shading effect at frosting state. The transmittance is tested as 90% at the clearing state and is merely 9% at the frosting state, and the contrast is 10:1.
The texture is observed by using a microscope, and the liquid crystal is the smectic E liquid crystal, has compact arrangement of crystal domains, and has a good shading effect at the frosting state. The transmittance is tested as 90% at the clearing state and is merely 9% at the frosting state, and the contrast is 10:1.
The texture is observed by using a microscope, and the liquid crystal is the smectic F liquid crystal, has compact arrangement of crystal domains, and has a good shading effect at the frosting state. The transmittance is tested as 90% at the clearing state and is merely 9% at the frosting state, and the contrast is 10:1.
The texture is observed by using a microscope, and the liquid crystal is the smectic G liquid crystal, has compact arrangement of crystal domains, and has a good shading effect at the frosting state. The transmittance is tested as 90% at the clearing state and is merely 9% at the frosting state, and the contrast is 10:1.
The texture is observed by using a microscope, and the liquid crystal is the smectic H liquid crystal, has compact arrangement of crystal domains, and has a good shading effect at the frosting state. The transmittance is tested as 90% at the clearing state and is merely 9% at the frosting state, and the contrast is 10:1.
The texture is observed by using a microscope, and the liquid crystal is the smectic I liquid crystal, has compact arrangement of crystal domains, and has a good shading effect at the frosting state. The transmittance is tested as 90% at the clearing state and is merely 9% at the frosting state, and the contrast is 10:1.
The transmittance is tested as 90% at the clearing state and is 15% at the frosting state, and the contrast is 6:1.
The transmittance is tested as 90% at the clearing state and is 15% at the frosting state, and the contrast is 6:1.
The transmittance is tested as 88% at the clearing state and is 11% at the frosting state, and the contrast is 8:1.
The transmittance is tested as 90% at the clearing state and is 15% at the frosting state, and the contrast is 6:1.
The transmittance is tested as 90% at the clearing state and is 15% at the frosting state, and the contrast is 6:1.
The transmittance is tested as 90% at the clearing state and is 15% at the frosting state, and the contrast is 6:1.
The transmittance is tested as 90% at the clearing state and is 15% at the frosting state, and the contrast is 6:1.
The transmittance is tested as 90% at the clearing state and is 15% at the frosting state, and the contrast is 6:1.
The transmittance is tested as 90% at the clearing state and is 15% at the frosting state, and the contrast is 6:1.
Application of the High Scattering Smectic Liquid Crystal Material of the Present Invention in Display
A display device that uses a high scattering smectic material mainly includes a display layer, as shown in
In general, the display layer is provided with a back layer on the back; in order to achieve color display, a color film is provided between the display layer and the back layer; in order to optimize the optical structure of the display, a light enhancing layer is provided between the display layer and the back layer, and the light enhancing layer includes a light enhancing base plate and a light enhancing member.
The light enhancing base plate is a high molecular film or glass; and the light enhancing member is a light enhancing film or prism structure.
The light enhancing member may be disposed on a surface of the light enhancing base plate facing the display layer and/or the back layer, or may be disposed on a surface of the first base layer facing the light enhancing layer or/and on a surface of the second base layer facing the light enhancing layer.
The light enhancing layer is designed to reflect and refract the light incident into the display multiple times, to increase the number of times and the amount of the light incident into the display layer, so that more light is refracted in the portion of the display layer corresponding to the pixel points that are required for displaying in the frosting state, thereby improving the scattering effect and enhancing the luminance at the pixels in the frosting state, and significantly improving the contrast between the pixels in the frosting state and the pixels in the full clearing state.
The display layer is shown in
The Mixed Layer of the Smectic Liquid Crystal Material
The mixed liquid crystal layer is generally formed by mixing the above high scattering smectic material, a conductive materials, a spacer and sometimes a polymer.
1) The mixed layer is formed by mixing the above high scattering smectic material, a conductive material and a spacer.
The smectic liquid crystal may be the high scattering smectic liquid crystal material of the present invention.
The spacer is a spacer ball or spacer rod made of a polyester or a polystyrene or a glass material.
The composition of the mixed layer is: the high scattering smectic material of 0.0002% to 99.99%, the conductive material of 0.0001% to 10%, and the spacer of 0.0001% to 90%, based on the total weight of the mixture.
2) The mixed layer contains a mixture encapsulated in the polymer structure and formed by the high scattering smectic material, a conductive material and a spacer:
The smectic liquid crystal may be the high scattering smectic liquid crystal material of the present invention.
The spacer is a spacer ball or spacer rod made of a polyester or a polystyrene or a glass material.
The polymer structure is formed by a monomer material or polymer material, and is directly printed or etched or nano-imprinted or jet-printed on an inner surface of a corresponding layer, and is thermally or UV cured into a polymer material having a given structure. The monomer material is any one of an epoxy resin monomer, a polyacrylate monomer or a polymethacrylate monomer.
The composition of the mixed layer is: the high scattering smectic material of 0.0002% to 99.99%, the polymer material of 0.0001% to 80%, the conductive material of 0.0001% to 10%, and the spacer of 0.0001% to 80%, based on the total weight of the mixture.
The polymer structure forms an accommodation cavity for accommodating a mixture formed by the high scattering smectic material, the conductive material and the spacer, and the polymer structure is in the form of regular ball, micro-cylinder, fiber, hemisphere, parallel strip, cube, rectangle, cross-wire form, network structure, square grating structure, irregular polygonal structure, or any of combinations thereof. The polymer structure is uniform or non-uniform, and is miscible or dispersible with the high scattering smectic material, the conductive material and the spacer, or contacted or spaced with the high scattering smectic material, the conductive material and the spacer.
The high scattering smectic material of the present invention may also be filled between two plastic films or two pieces of glass having a conducting layer to serve as a dimming medium, and may be filled in vacuum into a lattice screen to serve as a display device.
In order to control the thickness of the crystal liquid cell, in the high scattering smectic material of the present invention, a spacer ball or spacer rod made of polyester or polystyrene—or a glass material may be added; in order to reduce the working viscosity and improve the bonding firmness of the liquid crystal cell, a prepolymer may be added in the high scattering smectic material; and in order to achieve the effect of color display, a dichroic dye may be added in the high scattering smectic material.
The high scattering liquid crystal material of the present invention is applied to a smectic display device, so as achieve the application of the high scattering liquid crystal material in a display, by means of the excellent optical structure and drive method of the smectic display device. Application of the high scattering liquid crystal materials can provide a smectic liquid crystal display having an excellent optical structure.
The application of the high scattering smectic material of the present invention is not limited to using as the material in the dimming medium or a display device, and the high scattering smectic material of the present invention can be used in all of the devices with a dual-frequency drive mode of low-frequency frosting and high-frequency clearing.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011 1 0451207 | Dec 2011 | CN | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CN2011/085036 | 12/30/2011 | WO | 00 | 9/3/2013 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2013/097181 | 7/4/2013 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 8366964 | Maeda et al. | Feb 2013 | B2 |
| 20110260104 | Maeda et al. | Oct 2011 | A1 |
| 20140160384 | Li et al. | Jun 2014 | A1 |
| Number | Date | Country |
|---|---|---|
| H1077476 | Mar 1998 | JP |
| 2002146353 | May 2002 | JP |
| 2011090858 | May 2011 | JP |
| Entry |
|---|
| Halation Photonics Corporation, International Search Report, PCT/CN2011/085036, Oct. 4, 2012, 3 pgs. |
| Number | Date | Country | |
|---|---|---|---|
| 20130342775 A1 | Dec 2013 | US |
