TW379290B - Bistable nematic liquid crystal device - Google Patents

Abstract

A bistable pneumatic liquid crystal device comprises a layer of a pneumatic or long pitch cholesteric material contained between two cells walls. One or both walls are surface treated to provide two stable alignment directions into which liquid crystal molecules may switch under the influence of an applied electric field. This surface treatment also provides pretilt to the molecules and the pretilt angle may be different for the two alignment directions. The invention improves the switching by removing inelastic aximuthal memory anchoring energy and reducing azimuthal and zenithalanchoring energy of liquid cyrstal molecules at the cell walls without substantially changing molecular pretilt angles. The reduction in anchoring energy may be by a treatment to the cell walls or by an additive in te liquid crystal material. The treatment and additive may be an oligomer or short chain polymer applied to the wall prior to assembly in a cell, or as an up to 5% additive. The oligomer may be UV cured Norland N65 or -[S(CH2)6SCH2CH2O(CH2)6OCH2CH2]n-, HDVE (Hexane-1,6-diol di(vinyl ether), BVE (butyle viyl ether), EGTG(ethylene glycol bis(thioglycollate)), NDT (Nonane-1,9-dithol).

Description

3826pif.d〇c / 〇〇6 A7 H7 ------------------------- 5. Description of the invention (/) The present invention is related to a kind of bistable Bistable nematic liquid crystal device. A typical liquid crystal device is a liquid crystal material containing a thin layer between the cell walls. A transparent electrode structure is provided on the cell walls. An electric field can be applied through the liquid crystal layer to realign liquid crystal molecules. Three types of liquid crystal materials are known, nematic, cholesteric, and smetic 'each having a different molecular arrangement. The present invention relates to devices using nematic materials. In order to provide a large number of addressable elements to provide a display, generally one of the electrodes on the single wall is made into a column electrode in series, and the other electrode on the cell wall is made into a row electrode in series. These form x, y matrices of addressable elements or pixels. And in twisted nematic devices, the rms. Addressing method is commonly used for addressing. Printed by " Part I Central Government Bureau II Consumer Cooperatives L ------- f ^-(诮 Read the precautions before filling in this page) Twisted nematic and phase changes of Yijing device Types can be switched to the ON state when an appropriate voltage is applied, and can be switched to the OFF state when the applied voltage drops below a lower potential. These devices are monostable. An advantage of a nematic device is that it requires relatively low voltage. At the same time, it is mechanically stable and has a wide operating temperature range. Therefore, it is possible to make a small-sized and use a battery-powered display. The disadvantage is that the monostable switching characteristics of this device will limit the number of scan lines for multiplexed addressing. Another way to address large displays is to use a bistable liquid crystal device. A ferroelectric liquid crystal display can be combined with a nematic liquid crystal material and an appropriate cell wall surface alignment treatment to make a bi-stable device. This device is a surface-stabilized ferroelectric liquid crystal device (surface 5 $ Zhang scale applicable to Chinese National Standard (CNS) Λ4 ") — --- 3826Pif.doc / 006 A7 --- 157 I. V. Description of the invention (of ) Stabilised ferroelectric liquid crystal device '(SSFELCD for short), its description can be found in: LJ Yu, H Lee, CS Bak and Μ M Labes, Phys Rev Lett 36, 7, 388 (1976); RB Meyer, Mol Cryst Liq Cryst. 40, 33 (1977); n A Clark and ST Lagerwall, Appl Phys Lett, 36, 11, 899 (1980). One disadvantage of ferroelectric devices is the considerable voltage required to switch this material. This high voltage can make small, portable, battery-operated displays expensive. At the same time, these displays have other problems, such as a lack of shock absorption, a limited temperature range, and electrical-induced defects such as needles. If a bi-stable switching characteristic can be achieved using a nematic liquid crystal, the manufactured display may have the advantages of the various technologies mentioned above without its problems. Printed by the Central Bureau of Standards, Shellfish Consumer Cooperatives (please read the back-intentions before filling out this page)

Durand et al. Have shown that nematic liquid crystals can be switched between two alignment states by using chiral ions or flexoelectric coupling: A Charbi, R Barberi, G Durand and P Martinot-Largarde, patent Patent Application Number: WO 91/1 1747, (1991) "Bistable electochirally controlled liquid crystal optical device", G Durand, R Barberi, M Giocondo, P Martinot-Largarde, Patent Application Number: WO 92/00546 (1991 ) "Nematic liquid crystal display with surface bistability controlled by a flexoelectric effect" ° US Patent No. 4,333,708 describes a multi-stable liquid crystal device that provides an array of singular points on its cell walls. This substrate structure provides guidance The multi-stable structure of the director orientation, because the paper size of the wrong book is applicable to the Chinese National Standard (CNS) AdAL #, (21〇 × 29 · 7 ': Μ /) 3826pif.doc / 006 Μ B7 V. Description of the invention ( 3) (disclination) must move to switch between stable structures, which switch is achieved by applying an electric field. Patent application number: WO 97/14990, (PCT-96 / 02463, GB95 21106.6) describes a bi-stable nematic device with a grating surface treatment, so that at least one cell wall can allow nematic liquid crystal molecules to be received (adopt ) Either of two pretilt angles in the same azimuthal plane. The liquid crystal cell can be electrically switched between these two states to allow information to be displayed and remain unchanged even after power is removed. Another bistable nematic device is described in GB.2,286,467-A. It precisely forms a bigratmg on at least one cell wall. When an appropriate electrical signal is applied to the electrodes of the liquid crystal cell, such as DC coupling to a flexoelectric polarisation, this double-barrier allows liquid crystal molecules to accept two different angle alignment directions, such as patent application number: W0.92 / 00546 Narrative. Because the directors are quite close in these two separate states, the coupling between the director and the curved element can be small on the surface of the liquid crystal layer, which may hinder switching in some cases. The central government bureau of the Ministry of Economic Affairs, the Ministry of Economic Affairs and the Fifth Cooperative Press printed the meal (the neighbor first read the back, and the Jiang Yi matter and then fill out this page), the v- ° GB2286467-A bistable device also has no appearance in ferroelectric devices The other problem is that the surface layer of the molecule needs to be switched to eliminate the sUckmg effect. Surface layer switching usually requires high voltages, which results in high power consumption and special drive circuits. Therefore, the main purpose of the present invention is to provide a bistable 歹 ij liquid crystal device, which uses surface treatment to change the characteristics of the liquid crystal close to the surface, and reduces the energy of anchoring between the liquid crystal and the surface to reduce the problem of surface layer switching. This allows lower voltage operation without the need to include other devices. The paper size applies the Chinese National Standard (CNS) Λ4Μ!, #, (210X297) 3826Pif * d〇c / 006 A7 I_ B7 --------- ----------______________ 5. Description of the invention (shovel) parameters. To achieve the above and other objectives of the present invention, the present invention proposes a bistable nematic liquid crystal device including: two cell walls surrounding a liquid crystal layer composed of a nematic liquid crystal material; and an electrode structure on the two cell walls. A surface alignment on the two cell walls to provide alignment directions for the liquid crystal molecules; a device for resolving the switching states of the liquid crystal material; the invention is characterized in that a device is used for The inelastic azimuthal memory anchoring energy of the surface alignment is reduced. Ideally, this non-adaptive azimuth memory stabilization energy should be reduced to zero, and preferably the zenithal anchoring energy is also reduced. The device for reducing energy may be an oligomer or a short-chain polymer, which is coated on the surface or added to the liquid crystal material. It is preferable that the oligomer or short-chain polymer does not change the initial tilt angle by a substantial amount, for example, changes the initial tilt angle by more than 5 °. Printed by the Central Bureau of Standards of the Ministry of Economic Affairs and Consumers' Cooperatives (" Read the first note and fill in this I) This process is used in combination with a surface to produce a bi-stable nematic alignment. The bistable surface may be a surface-aligned double-barrier on at least one unit wall, which allows liquid crystal molecules to accept two different azimuth orientation directions. ) ° 8 Ρϋλ degree is applicable to China's "Yarn (CNS) Λ4_ (21〇X297, > in '3826pif.doc / 006 A 7 B7) V. Description of the invention (夂) The angle between the orientation directions can be 90. or less than 90 The fence can be a contoured layer of a photopolymer formed by a photolithographic process, for example, MC Hutley, Diffraction Gratings (Academic Press, London 1982) p95-125; and F Horn, Physics World · 33 (March 1993). Alternatively, double fences can be formed using emboss; MT Gale, J Kane and K Knop, J App. Photo Eng. 4, 2, 41 (1978), or ruled (ruling ); EG Loewen and RS WUey, Proc SHE, 88 (1987), or transferred from the carrier layer. The double fence can have a symmetrical or asymmetrical groove shape. In the latter case, its surface Alignment and initial stage Bevel, as described in GB2286467- A. The fence can be implemented on two unit walls, and each unit wall can have the same or different shape. Bistable surfaces can also use obliquely evaporated material (obliquely evaporated material) ), As described in patent application number WO 92/0054 (G Durand, R Barberi, M. Giocondo and P Martinot-Largarde, 1991). The cell wall may be substantially rigid, such as a glass material, or elastic , Such as polyolefin (polyoleHn). The electrodes can be formed as a series of columns and an array of electrodes, and can address the addressable elements or display pixels of the x, y matrix. Typically, the width of these electrodes is 200 μm, And the interval is 20μηι. In addition, these electrodes can also be arranged in other display formats, for example, (read first for the back; The printed paper size of the Jujube Bureau Consumer Cooperative is applicable to the Chinese National Standard (CNS) Λ4 Yue Jiang (210/2 boys and girls) Printed by the Consumers Cooperative of the Central Standards Bureau of the Ministry of Lithuania 3826pif.doc / 006 A7 H7 V. hair Description (Si) r-θ matrix or 7 or 8 display strip. In order to make the above and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is exemplified below and described in detail with the accompanying drawings. Brief description of the drawing Figure 1 is a schematic diagram of a matrix multiplexed addressing liquid crystal display; Figure 2 is a sectional view of the display of Figure 1; Figure 3 shows the threshold voltage of the random bistable switching of two liquid crystal cells: A function of the pulse wave length, one of which is a weak treatment and the other is a general strong treatment; and FIG. 4 shows an off-axis lithography architecture used to manufacture a fence structure having an asymmetric groove shape. As shown in FIG. 1 and FIG. 2, the display includes a liquid crystal cell 1 and a liquid crystal layer 2 composed of a nematic or long pitch cholesteric liquid crystal material between glass walls 3 and 4. Formed. The spacer nng 5 keeps the typical distance between the cell walls. In addition, there can be many beads of the same size dispersed in the liquid crystal to maintain accurate cell wall spacing. A strip similar to the column electrode 6 is formed on one of the cell walls 3, the column electrode 6 may be made of Sn02 or ITO, and a similar row electrode 7 is formed on the other cell wall 4. The m columns and n rows of electrodes form an mxn matrix of addressable elements or pixels. Each pixel is formed by the intersection of the column and row electrodes. The column driver 8 provides voltage to each column electrode 6. Similarly, the row driver (please read the precautions before filling in this page), 1T This paper is applicable to China National Standards (CNS) Λ4 ^ #, (210χ2π- : ΜΑ) 3826pif.doc / 006 A7 H7 V. Description of the invention (9) The actuator 9 provides a voltage to each row of electrodes 7. The applied voltage is controlled by the control circuit 10, which receives the power provided by the voltage source 11 and the clock provided by the clock circuit 12. Each side of the liquid crystal cell 1 has polarizers 13 and 13 '. The polarizing axes are arranged to substantially cross each other perpendicularly. In this state, the input polarizers are parallel to one of the alignment states, and the alignment states are 90 ° apart. Azimuthal angle. It is also possible to add an additional optical compensator similar to a stretched plastic film between the liquid crystal cell and one of the polarizers. A partially reflecting mirror 16 can be placed behind the liquid crystal cell 1 together with the light source 15 so that the display can be seen under reflection and can be illuminated from the back in a dim environment. In a transmission device, this mirror can be omitted. Du printed by the Central Bureau of Standards and Consumer Cooperation (read the precautions before filling this page),-° Before assembly, at least one of the unit walls 3 and 4 must pass through the alignment fence (alignment fence) grating) to provide bi-stable alignment, that is, two stable alignment directions of R and R ′ separated by 45 ° as shown in the figure, but it can also be 90 °. For example, this alignment can be provided by a symmetrical and asymmetrical double fence (Mgratmg) to give two alignments and the required initial tilt angle (pretilt). Techniques for producing a double fence to provide a bistable nematic device are described in the following articles: GB-A-2,286,467 (PCT-WO-95 / 22077) and WO97 / 14990, (PCT-96 / 02463, GB95 21 106.6). The second surface of the liquid crystal cell (if a double fence is not provided) can be treated with a planar or homeotropic monostable surface. The traditional alignment technology provides substantial stable energy (anchoring) to provide the paper size applicable to China's national standard. (CNS > / \ 4 said dry (210Xchuan 7.Convergence) 3326pif.doc / 006 A7 _—_— _ Η 7 V. Description of the invention (S) Initial tilt angle (zenithal) and orientation direction (azimuth), which means that the switching of this device is under the influence of the electric field, and as a result, most of the liquid crystal molecules move In the middle of the liquid crystal layer, the molecules located on and adjacent to the cell wall surface do not move. The initial tilt angle and alignment direction are required for good device performance. What is required is that the initial tilt angle and the alignment have both reduced Stable energy 'so that molecules located at or near the cell wall can move when a normal potential is applied. The invention provides such a required initial tilt angle and alignment while having a lower surface stabilization energy. The invention can achieve this An example is that the liquid crystal layer 2 contains oligomer units and it will preferentially move to the cell wall surface. The following is an explanation of the stable energy. Generally, the stability of nematic liquid crystal on one surface can be used Three macroscopic parameters are used to describe 'the initial inclination angle, apex stabilization energy, and azimuth stabilization energy. Consider a surface in the xy plane (parallel to a cell wall). The initial inclination angle (θρ) can be defined as Priority of the inclination and inclination of the nematic director to the xy plane. To change the inclination angle of the surface director from θρ to any inclination angle Θ, the energy W per unit area must be applied to this system [Α 经 满Printed by the Central Bureau of Standards and Labor, Consumer Cooperatives ^

(Jj »ll first read the ins and outs of v ± before filling in this page)

'1T

Rapini and M- Papoular, J. Phys. (Paris), 36, Cl, 194 (1975)] · W = W (! Sin2 (e-0p) (i) \ ^ is the vertex angle stabilization energy, which means that the surface needs to be changed The energy required for the inclination angle of the guide 90 °. If the guide has a preferential plane (in_piane) direction 'If along the X axis, an energy must be provided to the system to change its direction. Now this energy is determined by the following formula' This paper scale is applicable to the Chinese National Standard for Standards (CNS) Λ4 (210χ2ϋϋ 3 826pif. Doc / 006 A7 3 826pif. Doc / 006 A7 Printed by the Consumers ’Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs 52 I _______ B7 V. Description of the invention (^ ) W II \ νφ5ίη2Φ ⑵ where Φ is the change in the plane direction, and ~. Is the azimuth stabilization energy. The initial tilt and apex angle stabilization can be achieved by most solid surfaces, and azimuth stabilization usually requires some additional Processing to get priority plane direction, such as anisotropic polymer or surface fence. For most of the surface 'and Jia ① are very large, so only the high voltage can change the surface. Direction of the guide. Bistable The type nematic switching is determined by the direction of the surface guide, and in order to achieve low voltage switching, the above number must be reduced. Furthermore, the microscopic absorption caused by the first nematic layer entering the surface must be removed Any additional non-adaptive memory azimuth stability (P. Vetter et al., Euro Display 1993, SID, P · 9). This stable memory may have a fixed position (for example, between two switching states) ( pining) molecule, due to this effect, it may return to its original state after voltage is removed. Ideally, this memory should be completely removed so that after the voltage is removed, the 'molecule can still maintain the position after switching, but in fact, Reducing this memory is more satisfactory than removing it completely. The following three examples of weak anchoring treatment applied to a bistable surface are presented. Example 1 This treatment involves adding a small amount (1 ~ 10) before the liquid crystal unit is inserted. %) Of UV-cured adhesion material to the nematic. Examples of suitable materials include n65, N63, N60, or N123 (all of which are Norland Products Incorporated, This paper size applies to Chinese National Standards (CNS) Λ4 Yuege (210X297.) (Read first and then read the other side; 'I want to fill in this page and then fill in this page) "' 衣 订 3826pif.doc / 006 A 7 B7 _____ 5. Description of the invention (/ 〇)

North Brunswick, N], USA). In this particular example, one of these materials (N65) is used. In the first experiment, the concentrations of this material added to nematic E7 were 1%, 2%, 4%, and 6%, respectively. This mixture is then used to pierce the liquid crystal cell. The inside of the cell wall is a flat polymer layer coating without any orientation. The purpose of this experiment was to determine that the addition of N65 reduced surface stability. The surface is hardbaked to 160 ° C in advance using a photoresist layer (Shipley 1805) to ensure that it will not dissolve in the liquid crystal. Liquid crystal cells are manufactured using these surfaces with a gap of 10 μm. Each liquid crystal cell is filled with different concentrations of N65, including a control sample of pure E7. The insertion was performed at an isotropic phase (65 ° C), then slowly dropped to room temperature, and UV light was not used for irradiation. All liquid crystal cells exhibit a nematic random plane alignment, which is also called Schlerien texture. In the case of pure E7, 1% N65, and 2% N65, the fingertip pressure is applied to the cell wall, and the structure will not move. However, in the mixture of 4% and 6%, the structure has high mobility. And by applying a small amount of pressure, it is easy to move the domain boundary, and once the domain boundary is moved, it will no longer restore the original position, but will remain in the new position for several days. Therefore, a mixture of 4% and 6% can make memory disappear steadily. A second similar experiment was to expose the liquid crystal cell to UV radiation after it was filled until it was cooled to room temperature. In this case, 4%, 6%, and 2% of the mixture exhibited boundary mobility at room temperature. The improvement of the 2% mixture can be explained as follows. N65 material contains both ester and acrylic

U This paper size is applicable to China National Standards (CNS) Λ4 ^^ (210X297 liters age) (Read first and back ^ Italian matters #Fill this page), 1Τ Central Standards Bureau of the Ministry of Economic Affairs, Shellfish Consumer Cooperative, India Gas Λ7 Η 7 3 8 2 6pif .doc / 006 V. Explanation of the invention [acrylate monomer], which will polymerise to form oligomer units under UV radiation, and then combine together to form a comparative Large polymer chain. If 2% solution is cured—for a short time, the reaction will only stop when the oligomer unit has been formed. The oligomer does not separate from the liquid crystal (Phase separate), but they are easier to move to the surface to reduce the surface free energy as much as possible. This has the effect of diluting the number of liquid crystals on the surface, which can effectively reduce the order parameter S, which is defined as ( PG deGennes, The Physics of Liquid Crystals, Claradon Press, Oxford 1974): 5-i ((3cos2 ^ -l)) (3) The decrease in nematic order is due to the dual effect of oligomer concentration on filtering liquid crystals from the surface and Reduce compliance stabilization energy1, The former is to remove memory stability. Uncured materials also have this effect, but a larger concentration (> 4%) must be added, and the acrylate monomer does not tend to move closer to the surface. Then the liquid crystal cell is removed to contain 2 % N65 curing material, which is cured in the liquid crystal cell, and is used to fill another liquid crystal cell. The liquid crystal cell in the back also exhibits a highly mobile Schierien structure, showing a weak stabilization effect caused by the curing process It is caused by the additions in the bulk relative to any surface layer. The next set of experimental designs is used to show the effect of N65 treatment to stabilize the energy at the apex angle. This number can be measured by measuring the saturation voltage Vs Vs is the voltage at which the director in the liquid crystal cell is tilted perpendicular to the surface through the thickness of the liquid crystal cell. In fact, this is observed between crossed deflectors. When the transmission density of the Schierien structure is observed ( transmitted This paper size is subject to Chinese National Standards (CNS) () (¾ Read the Vi-Italy and then fill in ': This page) D Consumption of the Ministry of Economic Affairs, Central Standards Bureau . Cooperatives detent plate 3826pif.d〇c / 006 Λ7 V. invention is described (Shu ι) intensity) reaches zero is the measured We obtained by the following equation:

'17 3_85a / b7 ^ ;. VS WH * ---- (4) where d is the thickness of the liquid crystal layer, k, is the constant of the liquid crystal elasticity (spiay elastic), and is the dielectric anisotropy of the liquid crystal (permittivity anisotropy). The results are shown in Table 丨. Among them, the pure E7 liquid crystal cell cannot display a black state before the liquid crystal cell collapses, so only a lower limit of% can be given. In the case where E7 contains N65, curing is performed in a fused silica cell before the mixture is converted into a separate measurement liquid crystal cell. Exposure was performed using an unfiltered mercury lamp, and its light output was 2.0mW / cm2 〇 (read the meaning of the matter first and then fill out this page) The curing time of the liquid crystal cell mixture (minutes) W ^ Nm'1 ) Pure E7-> 5χ10 · 2 E7 5 with 2% Ν65 5 5.4x10-3 E7 with 2% Ν65 10 6 · 3χ10-3 E7 with 2% Ν65 30 7.7 x 10 · 3 E7 + with 2% Ν65 Pure E7 (l: l) 10 8.0x10'3 A table 1. The effect of the presence of N65 on the surface corner angle stable energy, 1T printed by the central department of the decorator # 贝 局 贝 工 consuming cooperatives. The solidification time will produce stronger stability. As a result, the formation of the polymer chains with longer polymer chains will tend to be separated from the nematic instead of lowering its surface order parameter. One set of data shows that the stable energy can also be adjusted by diluting the N65 / E7 mixture in pure E7. This paper ruler is in use " " National Standard (CNS) λΤ 说 松 (210 × 297λ >#) 3826pif.doc / 006 A7 Η 7 ____ 5. Description of the invention (/ >) In all cases, The percentage of N65 during the curing process was maintained at 2% to ensure consistent reaction kinetics. The above results confirm that N65 can make the planar memory disappear steadily, and reduce the apical angle stabilization energy (about a degree of magnitude). The next stage is to test the effect of this process on the switching of the bistable nematic device. An example of a surface that can provide bi-stable nematic alignment is a surface double fence made in a manner similar to that shown in Figure 4 (as described in GB2286467-A). In this case, the sample was manufactured by spin coating 1805 photoresist 20 onto IT0 coated glass 21 with a rotation speed of 3000 rpm and a coating thickness of 0.55 μm. This sample was then softbake at 90 ° C for 30 minutes. This double fence is exposed through the mask 22 using hard contact photolithography (that is, perpendicular to the surface of the mask 22, rather than 60 as shown in Figure 4). Its typical exposure time is 250 Printed by the Ministry of Economic Affairs, Central Bureau of Standards, Ministry of Industry and Commerce, Co-operative Cooperatives --------- ((Read the precautions on the back and fill in, fill in I) seconds (at 0.3 mW / cm2). The mask 22 includes a double-fence model, which is a chrome grid of 0.9 μm separated by a gap of 0.5 μm, giving a pitch of 1.4 × 1.4 μm in each direction. Development (devdopmerU) was then carried out in Shipley MF319 for 10 seconds, followed by rinsing with water. Finally, after the first deep UV exposure to preharden the photoresist (3_36 J / cm2 at 254_), the sample was baked at 160 ° C for 45 minutes. This process creates two double fences with the same modulation, each with a symmetrical shape. Therefore, the nematic alignment above it is expected to be two apart. Azimuth nontllted alignment state (alignment, but no surface tilt). Such an alignment is not the alignment used in general displays, but for testing and comparison purposes. 17 ^ The paper size applies the Chinese standard (CNS (210χ297 * ί)) 3826pif.doc / 006 Λ7 B7 V. Description of the invention (4) Therefore, a liquid crystal cell with a 0.95 μηι cell gap is produced on the two internal surfaces. The arrangement of these (early zero inclination angles) double barriers is that the groove direction on one surface is consistent with the groove direction on the other surface. E7 nematics with different concentrations of N65 are inserted into these liquid crystals with their isotropic phases. In the cell, all the liquid crystal cells exhibit two orientation directions as expected when they are cooled to room temperature. And these states have no initial surface tilt angle, and therefore no oblique angle. They do not pass the applied electrical pulse wave but only You can choose a state method (like the curved electrical coupling of the oblique angle structure). However, random switching between states may occur, which is seen through the area boundary movement induced by the pulse wave. There will be variable pulse wave length A rectangular unipolar pulse wave is applied to each liquid crystal cell. The polarity of each pulse wave is opposite to the previous pulse wave to maintain DC balance. The pulse wave is a time zone 100 times the length of the pulse wave. Separate. There is a voltage at each pulse length, which causes the area boundary to move. Figure 3 shows the relationship between the threshold voltage of two liquid crystal cells and time; one of the liquid crystal cells is pure. E7, while the other liquid crystal cell is doped with a mixture of E7 with% 2 pre-cured N65. At a pulse of 10.8ms, N65 obviously has a lower threshold voltage, only 5.〇ν / μιη. In contrast, pure The E7 liquid crystal cell exhibits a relatively high voltage switching (15.OV / um), and in fact, it needs to withstand dielectric breakdown at low pulse lengths. The above results show that N65 processing can obtain a low-voltage bi-stable switching, which Compatible with low vertex angle stable energy combined with non-planar memory stability, in addition to adaptability (elasUOW. Affected by double fences. 18 This paper size applies to China National Standards (CNS) (210X29WM 丨 :) (Read the legal meaning on the back first) Please fill in this page for further information) '1T The Central Standards Bureau of the Ministry of Economic Affairs, only the Consumer Cooperative Cooperative Seal 3826pif.d0c / 006 A7 B7 ___ V. Description of the Invention (K) In order to obtain a completely selectable bistable switching' must The applied pulse wave gets a state. This can be achieved using a DC scale connected to a curved electric deflector, provided that the two bistable states have a proper initial tilt angle. In WO 92/0054, the initial tilt angle can be used by Obtained by obliquely evaporating Sl. — A more controllable method, described in GB2286467-A 'Using ~ double fences to achieve the initial tilt angle, in which two modulations have an asymmetric shape. This method allows a bistable state One of them has a typical initial inclination angle of 17. and the other state maintains an initial inclination angle of 0 °. These surfaces were tested in combination with N65 treatment using a subsequent manufacturing process as shown in Figure 4. As described above, a thin 1805 photoresist layer 20 is spin-coated on the ITO-coated glass 21. After the soft baking, the photoresist layer 20 is exposed through a 1.4 × 1.4 μm pitch mask 22, and the off-axis diagonal exposure geometry is used as shown in FIG. 4; Expose at about 60 ° between normals and at about 45 ° to the mask array of square pixels. The exposure time was set at 540 seconds (at 0.15 mW / cm2). After development and processing, a double fence is formed on the opposite side of the flat photoresist surface (that is, without a fence and therefore without an initial tilt angle), and a liquid crystal cell gap of 10 μm is used to allow the initial surface tilt angle to be measured on the surface of the dual fence. Table 2 shows that different mixtures were incorporated into the liquid crystal cell, and then a crystal rotation method was used (TJ Scheffer and J. Nehring, Appl. Phys. Vol. 48, no. 5, p. 1783 (1977)) The initial tilt angle of the measured tilt state. In all cases, the non-inclined state has 诮 read the intent of the matter first and then fill out the straight,),-° by the "quotation of the '-Ministry Central Standard" and printed by the Bureau of Labor and Consumer Capital Cooperatives ^

This paper size applies to China National Standards (CNS) (210x2 < ^ > ^) 5. Description of the invention (/ 6) Initial tilt angle less than 0.Γ 3 8 2 6 pif .doc / 0 0 6 Α7 Η 7 The mixture inserted into the liquid crystal cell initially tilts pure E7 17.5 E7 + 2% Ν65 + pure E7 (l: l) 17.1 E7 + 2% Ν65 + pure E7 (2: l) 15.4 E7 containing 2% Ν65 2.2 Table 2. Ν65 The effect of the existence of the initial tilt angle of the surface. As expected, pure Ε7 gives a high initial tilt angle, but the addition of 2% Ν65 (pre-curing) results in a huge loss of the initial tilt angle, which represents this The initial tilt angle to achieve DC sensitivity. However, by adding pure E7 to further dilute the 2% mixture, the initial tilt angle can be brought closer to the pure E7 liquid crystal cell. (Printed by the Central Bureau of Standards of the People ’s Republic of China for consumer cooperatives " Read the notes on the back first and fill out this page)

1T compares the data in Tables 1 and 2 and shows that it is possible to obtain a mixture that can provide weak apex angle stability and maintain the initial surface tilt angle. The initial inclination angle loss of Ε7 containing 2% Ν65 can be explained as follows, the percentage is more weakened, and the non-tangential direction is allowed to be accepted on the local surface. Compared with the low initial inclination angle state, this will make the high initial inclination angle state become Restless. A description of this state can be found in GB95026357, "Uqmd crystal devke alignment'1, GP Bryan-Brown, CV Brown and DGMcDonnell. The examples shown above are examples of how to use oligomer additives (N65) and typical orientations. Columns (such as E7) to enhance the bi-stable nematic loading. 20 This paper is applicable to the Chinese National Standard (CNS) (210X29D > »). Five A7 H7 1.2, 2 pif.doc / 〇〇6, description of the invention (/?) The voltage response of 4 does not include other surface parameters such as the initial tilt angle. Another example of weakly stable treatment is the use of thiol (th101) and vinyl ether (vinyl ether) block copolymers (block polymerisation) to form the structure A shown below, where the subscript n is a repeated number in the chain.-[S (CH2) 6SCH2CH2〇 (CH2) 6OCH2CH2] n -.... A as example 1 , Adding a precursor material to E7, and then curing in a fused silica pre-cell. Then the converted mixture is transferred to a second liquid crystal cell, whose internal surface is hard-bake Anti-shovel film. Refilling is performed at 65 ° C, then slowly Cool to room temperature. The mixture of ~ specific liquid crystal cells is obtained by solidifying 5 solution-free E7 containing the precursor material. This liquid crystal cell shows that the schlerien structure has a highly mobile region demarcation, confirming that all plane memory stability has been lost The measurement of its saturation voltage shows that its apex angle stable energy is lower than the 値 of MPNπΓ1, and even lower than that shown in Table 1, indicating that the oligomer unit formed in this case can more effectively reduce the surface of the nematic phase Sequence parameters. Dilute the 5% solution to pure E7 again, the hydrates that are not apparent on the surface of the fence, have a weak apex angle and combine with a high (> 15 °) initial tilt angle. Therefore, Structure A is another successful example You can add oligomers to the nematic (such as E7) to improve the voltage response of the bistable nematic device 'including other surface parameters such as the initial tilt angle. 2 1 (Please read the remarks on the back first Fill in KT page) No, ys 51 (CNS) (210X 2 ^ 7λ > ^ 3826pif.doc / 006 A7 3826pif.doc / 006 A7 Central Bureau of Judicial Bureau, Ministry of Economic Affairs) Printing Engineering Co-op "? H __________- five instructions (? I) of the invention, the following structures B is a list of example monomers' can also be constructed with a weak stabilization processing. CH2 = CH 0 (CH2) 60 ch = ch2 HDVE (Hexane-l, 6-diol di (vinyl ether)) ...... B (hexane-1,6-bis alcohol bis (vinyl ether)) CH2 = CHOC4H9 BVE (Butyl vinyl ether) .... B (Butyl vinyl ether) HSCH2C02 (CH2) 20C0CHS2H EGTG (Ethylene glycol bis (thioglycollate)) .... B (Ethylene glycol bis (thioglycollate))

HS (CH2) 9SH

NDT (Nonane-l, 9-dithiol) .... B (nonane-1,9-bisthiol). The previous examples have shown that a lower voltage bistable nematic switch can be produced when Wq is reduced. Therefore the materials in B must be studied to understand their effect on \ ¥ 0. The mixture of these materials is first cured and then added to the liquid crystal. The final mixture is tested in a liquid crystal cell with a flat hard baked photoresist on its internal surface, as described in Example 1. Then we use the method described in Example 1 to get We's 値.

Among the materials listed, EGTG and NDT are monomers with thiol terminus, while HDVE and BVE are difunctional (difunctionai) and monofunctional (ene) materials, respectively. Q 22 This paper The standard is applicable to the Chinese national standard (CNS) Songsong (2) 〇xIGΆ '] (诮 Read the precautions before filling in this page) ^.' Π 3826pif.doc / 006 A7 Η 7 V. Description of the invention (丨?) The first set of intensive mixtures is shown in Table 3. In each case, different proportions of monofunctional BVE were added to the bifunctional HDVE to produce chain termination and to form smaller molecular oligosaccharides. Polymer. In each case, the percentage quoted is the molar quantity of BVE relative to HDVE. Furthermore, the amount of NDT in each mixture was changed to maintain the thiol group and ene Equal number of groups. Each mixture is added with 1% Igracure 651 (Merck) as a photoinitiator. For each material, curing is performed for 10 minutes under a mercury lamp (2.0 mW / cm2) E7 (Merck) is regarded as liquid crystal, 2% of each material is added (By weight). The results in Table 3 show that the apex-stabilizing energy produced is in the range of 3.6-8.8xl (r3Jm_2. Therefore, all mixtures can be regarded as being able to successfully reduce the stability of pure E7 (> 5xlO_2Jm_2). . Further, adding more BVE can make the oligomer chain shorter and can be found to lead to weaker stability. Material WexlO'3Jm-2 NDT / HDVE / 2% BVE 8.8 NDT / HDVE / 5% BVE 5.9 NDT / HDVE / 20% BVE 3.6 Table 3. Measurement of apex angle stability of a thiol / diene system with chain ends. 値 Further tests for the stability of a given material type and the correlation of molecular length are performed using a set Includes a mixture of EGTG, HDVE and BVE. 23 This paper size applies to the Chinese national standard (CN ^ T ^ 疋 梠 (2 丨 0 X " 5 -— (" Read the back of the first: > J · Implementation of different meanings) , ¾ page)

、 1T Printed by the Consumers ’Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs _ -—— · —— * · **** " '1 _. — — · * 3826pif.doc / 006 _ -—— · ***** * " '1 _. — — · * 3826pif.doc / 006 Printed by the Consumers' Cooperative of the Central Bureau of Standards of the Ministry of Economic Affairs. 5. Description of the Invention (Work) In this case, 'Perform GPC analysis to measure the molecular weight of the parent material'. The results are shown in Table 4; Mn is the average number of each chain 'Mw is the average weight of each chain, and 1 is the vertex angle stabilization energy. It is indeed found from this that the smallest part (2%) of BVE has the longest molecular weight 'and vice versa. Add 1% of each material to E7 and measure We. Considering the error of% measurement, the correlation of We on molecular weight is quite perfect ° Material Mη Mw We xl0_3Jm · 2 EGTG / HDVE / 2% BVE 12640 27330 10.9 EGTG / HDVE / 5% BVE 6970 17140 5.3 EGTG / HDVE / 10 % 5000 11550 6.6 BVE 2900 6200 4.4 EGTG / HDVE / 20% BVE --- Table 4. Measurement of apical angle stability of a thiol / diene system with chain ends. In summary, both groups of materials studied in this example are It can be found to reduce We. More samples of these materials have also been found to reduce the switching voltage of bistable nematic devices. Although the present invention has been disclosed as above with a better reality, it is not intended to be used as an inventor of this invention. Anyone who learns this bribe will not be able to dismiss the spirit and scope of the invention. The scope of protection of ㈣ shall be determined by the scope of the attached patent claims. This paper size applies to the Chinese National Standard (CNS) A4ML 枋 (210x ^ 7 ^ · ^ ----------- (Please read the following ^ -Implementation before filling in this page) 'π

Claims (1)

# 82 乘 b7i2i〇. Doc / 0 06 A8 B8 C8 D8 Advantage 1. A bistable nematic liquid crystal device that can be switched between two different stable states. The bistable nematic liquid crystal device includes: two A cell wall surrounds a liquid crystal layer composed of nematic liquid crystal material; an electrode structure on the two cell walls; a surface alignment on one or two cell walls to provide a number of surface initial tilts for the liquid crystal molecules Two orientation directions of the angle; a device for distinguishing the switching states of the liquid crystal material; the invention is characterized in that a device is used for recording the non-adaptive azimuth angle of the surface orientation on one or two cell walls Reduced stabilization energy. 2. The bistable nematic liquid crystal device 'as described in item 1 of the patent application scope further includes a device for reducing the vertex angle stabilization energy. 3. The bistable nematic liquid crystal device described in item 1 of the scope of patent application ^ 'wherein the device for reducing the stable energy is an oligomer or a short-chain polymer, which is coated on the surface or Added to the liquid crystal material. 4. The bistable nematic liquid crystal device as described in item 3 of the scope of patent application, where the oligomer is selected from the following materials: Norland N65 Printed by the Consumer Cooperative of the Central Bureau of Standards, Ministry of Economic Affairs (please first Read the notes on the back and fill in this page), 1T-[S (CH2) 6SCH2CH20 (CH2) 60CH2CH2) n-CH2 = CH 0 (CH2) 60 ch = ch2 HDVE (Hexane-l, 6-diol di (vinyl ether ) CH2 = CHOC4H9 BVE (Butyl viyl ether) HSCH2C02 (CH2) 20C0CHS2H 25 Til® Home Standard (CNS) A4 · (2) 297 male sauce S752S0 3826pif.doc / 006 A8 B8 C8 D8 Central Standard The Bureau of Work and Consumer Cooperatives printed six 'patent application scope EGTG (Ethylene glycol bis (thioglycollate)) HS (CH2) 9SH NDT (Nonane-l, 9-dithiol) 5. Double as described in item 3 of the scope of patent application The stable nematic liquid crystal device, wherein the weight of the oligomer is 10% of the liquid crystal material. 6. The bistable nematic liquid crystal device according to item 3 of the scope of patent application, wherein the chain length (η) is Less than 100 repeating units. 7. The bistable nematic liquid crystal device as described in item 3 of the scope of patent application, wherein the The type, concentration, and chain length parameters of the polymer are arranged to reduce the order parameters of the liquid crystal located at or adjacent to the cell wall. 8. The bistable nematic liquid crystal device described in item 3 of the scope of patent application, where The type, concentration, and chain length parameters of the oligomer are arranged to change the phase of the liquid crystal material located at or near the cell wall. 9. The bistable nematic liquid crystal as described in item 3 of the scope of patent application Device 'wherein the oligomer is pre-cured before entering one of the materials between the cell walls. 10. The bistable nematic liquid crystal device described in item 3 of the scope of patent application' where the oligomer is first input The single wall is then pre-cured as one of the materials. 11. The bistable nematic liquid crystal device according to item 1 of the scope of patent application, wherein the surface alignment is provided by a double fence surface. 26 Paper dimensions Applicable to China Gujia Standard (CNS) Α4 specification (2 丨 〇χ: 297mm) Binding > * (Please read the precautions on the back before filling this page}