JPH01500465A - lcd display - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] lcd display The present invention protects liquid crystal displays and liquid crystal displays against overvoltage. Regarding the method.

Liquid crystal displays (LCDs) are well known and have enjoyed great commercial success. There is. In a liquid crystal display, the liquid crystal material changes optically in response to an applied voltage that exceeds a threshold voltage. changes its state (i.e. becomes “on”), resulting in a change in the appearance of the display. This is due to its ability to easily identify. For example, the display is below the threshold voltage Above the threshold voltage, it appears opaque, and above the threshold voltage it appears transparent, or vice versa. Alright The display can change color when a threshold voltage is exceeded. LCD manufacturing In terms of applications, Bahadur is a molecular crystal. Talz and Liquid Crystals (Mo1. CrysL is! Mecha+s t,) 1, 9, 3 (1,984).

As the voltage applied to the LCD increases, at some point the voltage increases The liquid crystal is dielectric withstand of other material components, and its pillar 1) i hahe △ Yin ÷ 7 Kamomei Minia + Topu + 1 Rochibagpu? Image to Doo - Small voltage to withstand voltage Vw of LCD The voltage that exceeds the withstand voltage is called overvoltage. For example, when distributing voltage exceeding ■1 If the LCD is accidentally connected directly to a system that If the system connected to the LCD experiences an unexpected power surge, the LCD May be exposed to pressure.

For some applications with LCDs, such as battery-operated watches, the LCD is connected to low-voltage circuits, i.e. Used in circuits that operate below voltage. The supplied power is substantially equal to the voltage resistance of the LCD. It has been proposed to use LCDs in situations where pressure is exceeded. west germany Patent Application Publication No. 3゜308.972 (Heverhagen) Hagen et al.) describe a device that displays the actuation status of a fuse. Ru. LCDs with series connected capacitors straddle the fuse to be monitored. electrically connected. Connect both connecting leads resistively or One can be connected capacitively and the other resistively. Do it like this In order to detect the voltage of the main parts with almost no power required, the A small operating current is supplied.

West German Patent Application Publication No. 3,239,703 (Ker) ) describes electrical connectors for media and high-voltage cables and describes the connector An LCD monitor continuously reads the on/off status of the cable. The monitor is Connected to the power supply part of the cable via a voltage drop circuit. The monitor is Connected to the shield of a grounded cable. West German patent application published Specification No. 3,402,655 (G oehlich) A device is described that indicates the status of a voltage device. This device is an LCD electrically connected to the device by a single-phase connection line and connected to earth. Capacitively connected.

The present invention provides an electrical device comprising: (a) a positive dielectric anisotropic liquid crystal; The capacitance CI is below the voltage, and the capacitance C is above the saturation voltage. LCD with

as well as (b) Capacitance connected in series with the liquid crystal display and satisfying the inequality: It comprises a capacitor having C8. Preferably the capacitance C0 is substantially is constant. Also, C0 is the inequality: %formula% It is preferable to satisfy the following. The liquid crystal is preferably an encapsulated nematic liquid crystal.

In another aspect of the invention, an electrical device is provided, the device comprising: (a) series connected and (b) capacitance C0, inequality: % expression % In formula E, n is the number of displays in the array, and C3 has the same meaning as above. ] satisfies A capacitor connected in series with the LCD at the end of the array so that It consists of

In yet another aspect of the invention, an electrical circuit is provided, the circuit comprising: (a) the L CD.

(b) A capacitor in series with the LCD, and (c) a voltage lower than the withstand voltage of the LCD. Has a means of adding across the LCD display and capacitor combination It consists of

Preferably, the capacitor has a substantially constant capacitance; The passitance is preferably C1 or less, more preferably C0 to C2, and C1 or lower. and C6 have the same meanings as above. The circuit may have an additional LCD. The means is LC Even if the power supply has an output voltage lower than the withstand voltage of D or is combined with a voltage drop means. The power source may have an output voltage that is higher than the combined withstand voltage of the LCD. voltage drop The lower means may be a capacitor.

Figures 1a and 1b show how applied voltage aligns liquid crystal molecules in an LCD. This is schematically shown.

Figure 2 shows the capacitance of an LCD made from a liquid crystal with positive dielectric anisotropy. This generally shows how it changes with applied voltage.

Figure 3 shows an array of LCDs arranged to form a larger pattern. This figure shows the uniqueness of the present invention.

Figure 4 serves as a display element for an LCD or analog voltage display. 2 shows another embodiment of the present invention.

FIG. 5 shows a stacked LCD structure using encapsulated liquid crystals.

Figure 6 shows a stacked structure using liquid crystals, in which multiple LCDs are connected in series. forming a connected array.

When using a voltage drop circuit that drops the line voltage reaching the LCD, at the same time the L This has the disadvantage of substantially increasing the line voltage required to turn on the CD. example For example, consider an LCD with a threshold voltage of 10 volts and a withstand voltage of 200 volts. Line electricity If you connect the LCD to a voltage drop circuit that halves the line voltage, the line voltage will be at least 20 The LCD is exposed to a threshold voltage only when it is in port. In other words, the effective threshold voltage is doubled. The LCD becomes less sensitive than before. At the same time, the effective withstand voltage doubles, and the LCD It will not break down until the voltage between the two reaches 400 volts. Voltage drop circuit reduces line voltage to 1/3 If the voltage drops, the LCD will be exposed to the threshold voltage until the line voltage is 15 volts. do not have. That is, the effective threshold voltage does not increase in the first case. However, the line voltage At only 300 volts, the voltage across the LCD reaches 200 volts, i.e. , the level of protection against overvoltage is reduced. Therefore, the effective threshold voltage and the degree of overvoltage protection are There is a trade-off between increasing the effective threshold voltage while maximizing overvoltage protection. It is desirable to minimize the amount of

Typically, liquid crystals have long sleeves of molecules aligned or oriented parallel to each other. It is a molecule with a long and narrow shape. This alignment makes the liquid crystal anisotropic. this is, physical, optical and other measurements when measured parallel and perpendicular to the direction of alignment. It means that the properties of are not the same. The direction of alignment depends on some kind of external force, e.g. Can be easily affected by voltage. Figures 1a and 1b show that the LCD has this feature. Demonstrates common ways to use gender. LCDI has liquid crystal 2 between electrodes 3 and 4. It is connected across the power supply 5. Switch 6 is open and , the LCDI is in the "off" state. The liquid crystal 2 is oriented parallel to the electrode surface. It is depicted as having long sleeves and is compatible with "twisted nematic" type LCDs. but other orientations including random orientation depending on the type and structure of the LCD. Good too.

Although the power source 5 is shown as a DC power source, an AC power source can also be used.

Figure 1b shows the same device and circuit, but with switch 6 closed.

The voltage applied to the LCDI by the power supply 5 is This is sufficient to align the molecules of crystal 2 so that the long sleeves are vertical. Due to the anisotropy, There are differences when viewed perpendicular to the long axis (Figure 1a) and when viewed parallel to the long axis (Figure 1b). As a result, the viewer cannot tell whether the LCD is “off” or “on.” Easy to determine. For example, the liquid crystal 2 becomes opaque in the "Off-1" state, and becomes opaque in the "Off-1" state. Does it appear transparent, or vice versa?

Liquid crystals can also exhibit anisotropy in dielectric constant. In that case, eL in equation (1) The dielectric constant of liquid crystals, generally expressed, has two values: el and e.

is more accurately expressed using Here, e is a value parallel to the long axis, and C2 is the value perpendicular to the long sleeve. A liquid crystal with larger e than e has positive dielectric anisotropy. It is called having. Such liquid crystals typically include Rice) and nematic LC. Those used in D are included. Suitable positive dielectric anisotropic liquid crystals include British Commercially available from British DrLg Hocse liquid crystals known as C7 and benzoate esters, especially 4-cyanophyl Those having a phenyl group are included. A typical positive dielectric anisotropic liquid crystal is As described in US Patent No. 4,591,233 (Fergason) and is incorporated herein by reference.

Preferably, C0 is substantially constant under all applied voltages.

The structure of the capacitor does not matter. Dielectric materials include air, oil, paper, vacuum, and six-fluoride. It may be sulfur oxide, aluminum oxide, ceramic, etc.

The advantage of selecting C6 according to inequality (8) will be explained with reference to the case shown below. . C, is 10pP%C7 is aopp, Vt is 0 volts, Vw is 200 volts. Consider the default LCD. Table 1 shows that the capacitance C0 is 2.20 or 6 Showing what happens when this LCD is connected in series with a 0pP capacitor, The initial and final capacitances fall outside the range indicated by inequality (8).

Table 1 Capacitance Co (pF) 2 20 6O Line voltage 60 15] when LCD reaches VT, 1.7 LCD reaches V Line voltage 3200　500　When using 3002pF capacitor, overvoltage Although there is substantial protection against, LCD sensitivity is very slow. Line voltage is 6 It turns on only when it reaches 0 volts. When using a 60pF capacitor , the sensitivity of the LCD is very good (not significantly exceeding the normal threshold voltage of 10 volts). It turns on at a line voltage of 11.7 volts, but overvoltage protection is minimal. 20p When using a P capacitor, the LCD sensitivity is still good, even at 15 volts. It turns on at line voltage and also enjoys substantial overvoltage protection.

Also, within the range of C+Ct in inequality (8), the desired relationship between sensitivity and overvoltage protection is determined. It should be noted that C8 can be selected to fine-tune the balance of. C1 Choosing C8, which is close to C7, emphasizes the overvoltage protection more, while choosing C6, which is close to C7, When selected, the sensitivity of the device is more emphasized.

Also, if you want to mainly emphasize a specific function, you can choose something outside the range of inequality (8). It should also be noted that it is possible to For example, if you mainly focus on overvoltage protection , Co is the formula: % formula % (9) In fact, it may be less than or equal to 01.

The present invention is applicable to LCDs made from any liquid crystal having positive dielectric anisotropy.

In a preferred embodiment, the LCD is commonly known as "twisted nematic". For its production method and properties, please refer to the above-mentioned Bahadar literature. too In another preferred embodiment, the LCD is manufactured from encapsulated liquid crystal. This is a siege or 1 This is a liquid crystal confined within an encapsulating medium or material. The enclosed liquid crystal is and an encapsulation medium in which the liquid crystal does not dissolve, forming independent capsules of the liquid crystal in the encapsulation medium. It can be manufactured by forming. Contains pleochroic dye to appear colored good. A preferred encapsulation medium is polyvinyl alcohol. Where to carry out the invention Suitable encapsulated liquid crystals and devices made therefrom are described in U.S. Pat. No. 435.047 (Ferguson) and No. 4.591,233 (Ferguson) ).

The liquid crystal in an LCD does not have to be a single or pure component, but can be a mixture. This is well known to those skilled in the art. For example, liquid crystallization in a specific temperature range Or liquid crystals may be blended to achieve a certain degree of dielectric anisotropy. Honmei The term "liquid crystal" or "liquid crystal material" used in the specification refers to a single liquid crystal component or liquid crystal material. Includes crystal blends and encapsulated liquid crystals.

Implementation of the invention is limited to connecting a capacitor to a single positive dielectric anisotropic LCD. Not determined. Figure 3 shows that capacitor 8 with capacitance c0 is connected in series. This state is connected to the first LCD of the 29 positive dielectric anisotropic LCDs. 7, and each LCD shows C8 and C8 below Vt and above Vs, respectively. have equal capacitance of C7 and are arranged in an array forming the number l . (For simplicity, each LCD 9 is not marked in the drawing.) Multiple LCs When using D, the device must consist of an aluminum alloy made up of multiple liquid crystal elements. The first liquid crystal element is in an unenergized state with a capacitance lower than that of any other liquid crystal element. It is made of liquid crystal material with positive dielectric anisotropy and has a capacitance of As a result, the liquid crystal element has a capacitance in the applied state that is greater than its capacitance in the non-applied state. has a capacitance of a second liquid crystal element in electrical series with the first liquid crystal element; , the second liquid crystal element is connected to a capacitor of the first liquid crystal element in an applied state. It has a capacitance in the unenergized state that is lower than the current state. Each liquid crystal element has a positive dielectric It is preferable to have anisotropy. Moreover, in a similar alloy, the liquid crystal elements are virtually identical. They may have the same dimensions or different dimensions. This aspect of the array is identical to the present application. International Application No. PCT/US 87101756 filed on the same day by applicant (representative) It is listed in reference number MPI+34A).

Such a structure offers many advantages. Although each LCD is quite small , the overall appearance is that of a large display.

It is difficult to manufacture individual large LCDs, and once manufactured, there is considerable leakage. This is because the time constant for the required Vt due to the current flowing between the electrodes and the current flowing between the electrodes is quite large. , each consumes significant current or requires turn-on time. Structure of Figure 3 With construction, this problem can be avoided. LCD consists of n capacitors connected in series. – (in this case n is 29), and the total capacitance is Below the threshold voltage, C,/n, and above the saturation voltage, C=/n. the whole ca The capacitance of the array is much smaller than that of an individual LCD. It is even much smaller than the capacitance of a single LCD of comparable dimensions. Explain first As mentioned above, C0 can be selected to emphasize LCD sensitivity or overvoltage protection. subordinate Therefore, for sensitivity, c + / n < c o (io) On the other hand, for overvoltage protection, co<C1/n (11) is desirable.

Yet another aspect of the invention provides an analog voltmeter. In Figure 4, analog The voltmeter lO is connected to subunits 11.12.13 and 14 in parallel with each other. It consists of Each subunit has at least one capacitor connected in series with a capacitor 16. Both have one LCD 15. ■A subunit with an LCD of more than 15 In ports 12, 13 and 14, the LCDs 15 are connected in series with each other. Each L The CD 15 is made of positive dielectric anisotropic liquid crystal. To simplify the example, each The LCD 15 has an equal capacitance C0 below the threshold voltage Vt, and a saturation voltage Vs In the above, each capacitor 16 has an equal capacitance C1, and each capacitor 16 has an equal capacitance C1. C8. When connecting the voltmeter 10 across the voltage V, the analog ■Provide an outboard. n pieces with equal capacitance connected in series For capacitors, the total voltage is divided equally between them, and each It is known that it is responsible for the body's 17n. Therefore, all LCD15 in the subunit is formula (12):% formula%) [In the formula, n is the number of LCDs 15 in the subunit, ■o is the number of capacitors 16 and This is the voltage that increases. ] It turns on at a line voltage V given by . The voltage across each LCD 15 is Vt , then formula (13):% formula%) satisfy. Combining equation (12) and equation (13), V=Vt(n+C +/co) ct 4) is obtained. Therefore, for example, if Vt is 10 volts, If unit 11 is turned on at V=15 volts, subunits 12.13 and 14 are turned on at v-25, 35 and 45 volts, respectively.

In some cases, the visible part of the voltmeter 10 may be covered as shown by the dashed line 17. In this case, only the LCD within the dashed line will be visible, resulting in a single bar lead out. It becomes Those skilled in the art will appreciate that other structures and combinations other than those shown in FIG. It will be understood that this is also possible. For example, if necessary, from subunit 11 The increase in the number of subunits up to 14 does not have to be an arithmetic progression as shown in the figure. It may be a geometric or other progressional array. Alternatively, the key Capacitance C3, C! and C0 are the same for each LCD or capacitor. They don't have to be the same.

Yet another aspect of the invention protects LCDs from line voltage surges. this In embodiments, the normal line voltage is less than the withstand voltage of the LCD, but the LCD has a withstand voltage of Fragile to over surge. Capacitances C1 and C3 as defined earlier The LCD with a capacitor and the LCD and the capacitor are It is connected in series to means for applying a voltage equal to or lower than Vw. Capacitor has a constant capacitance Preferably, it has a sitance of C6. C0 is preferably less than or equal to C, 01 It is more preferable if it is above and below C7.

LCDs suitable for implementing the invention are advantageously of laminated construction using encapsulated liquid crystals. Ru. FIG. 5 shows a cross section of such a laminate 18.

The laminate consists of two opposing electrodes 21 and 22 each attached to the inner surface. transparent support materials 19 and 20. The encapsulated liquid crystal 23 and the support material 19 20 and between electrodes 21 and 22, forming an LCD 24. L The boundary of CD24 is electrode 2! and 22 overlapped portions. line 25 -25' and 26-26° are drawn to make these boundaries easier to understand visually. Ru.

This laminated structure is used when forming an LCD array connected in series as shown in Figure 3. Particularly advantageous. FIG. 6 shows a cross section of such a structure 27. two supporting materials 28 and 29 have electrodes 30a-d attached to their inner surfaces. Encapsulated liquid crystal material A material 31 is present between support materials 28 and 29 and between electrodes 30a=d and is Form D32a-c. The overlapping portion of electrodes 30a and 30b defines LCD 32a. The overlapping part of the electrodes 30b and 30c defines the LCD 32b, and the overlapping part of the electrodes 30b and 30c defines the LCD 32b. The overlapping portion 30d forms an LCD 32c. Visually identify LCD32a-c. To make it easier to read, the lines 33-33', 34-34°, 35-35°, 3fl 36°, 37-37° and 38-38''. The LCDs 32a=c are connected in series due to the overlapping part, and each electrode does not overlap. The sections form electrical connections between adjacent LCDs. For example, the electrode 30a or The part of electrode 30b that does not overlap 30c connects LCD 32a and 32b. do. Therefore, LCD 32a is connected in series with LCD 32b, and then LCD 32 b is connected in series to the LCD 32c.

An LCD having a laminated structure can be easily manufactured as follows. Desired electrode pattern Create a drawing of the Each drawing drawn using the normal photoresist method, e.g. For example, one side is coated with an electrode material such as indium titanium oxide (ITO). For example, polyethylene terephthalate (Mylar) or polyamide. Transfer to a sheet of transparent support material. Remove excess and unnecessary ITO to improve support material Leave a pattern of ITO electrodes on each sheet. For example, the knife coating method crystalline material, e.g. brite mixed with an encapsulating medium, preferably polyvinyl alcohol. Fish Drug House E63 or Merck 1840 Cover the conductor side of one sheet with Curing the adhesive layer of the liquid crystal-encapsulation medium mixture do. Place the other sheet on top of the encapsulated liquid crystal layer and place the conductor with the conductor side facing the liquid crystal material. Take care to ensure that the patterns match properly. Next, heat it with a heater. A laminated structure having a plurality of LCDs connected in series is obtained.

Examples of the present invention are shown below as examples, but are not limited to biphenyl-containing Nematic liquid crystal (E63, manufactured by British Drug House, West Germany) Merck subsidiary) 2g polyvinyl alcohol (vinol (V1nol) 203, Air Products Corporation (Ari Products) Corp., ), purified as described below) mixed with 4 g of a 22% aqueous solution of A high-impedance encapsulated liquid crystal was manufactured using this method. For small homogenizer with low shear The mixture was emulsified.

Set the doctor knife to 3 mil and apply ITO (Intrex). ) A polyester film (Mylar) with an electrode film is made by emulsion. coated. The emulsion was then air dried at room temperature. Align the electrodes properly With care, the second polyester film with the ITO electrode is attached to the first polyester film. It was placed against the emulsion side of the film. Between hot rollers (approximately 90°C) by heating the sandwich structure in a heater at about 90°C for 3 to 4 hours. For laminating polyester films together. The thickness of the encapsulated liquid crystal layer is approximately 10 microns. Met. The diameter of the nematic liquid crystal particles was approximately 3-4 microns.

An LCD with a cross-sectional area of about 1 cm" was manufactured from the laminate. The LCD has a zero-feel In the field-off section, the light is scattered. L CD has approximately 7 volts. It had a threshold voltage and a saturation voltage of about 35 volts.

The resistivity is 3 x 10' with a dielectric constant of 12 using ballistic measurements of decay time! Ω・c At m. The capacitance of the LCD is l volts (which is below the threshold voltage) approximately 1000 pF at 40 volts (above the saturation voltage). It was about 2000 pF.

The LCD was connected in series with a 1500 pF capacitor. In this combination, LCDs have an effective threshold voltage of about 10 pol I and an effective saturation voltage of about 100 volts. Shiotsu.

200g of polyvinyl alcohol was purified by washing with 500πg of methanol, and then Dissolved in 500 liters of deionized water. Add methanol 500x (l) to remove from solution Precipitate polyvinyl alcohol, then dry.

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Claims (16)

[Claims] 1. An electrical device, (a) Consists of positive dielectric anisotropic liquid crystal, has capacitance C1 below the threshold voltage, and has saturation. a liquid crystal display having a capacitance C2 above the sum voltage; and (b) connected in series with the display, inequality: C0<C2 A device comprising a capacitor having a capacitance C0 satisfying 2. 2. The device according to claim 1, wherein C1<C0<C2. 3. 2. The apparatus of claim 1, wherein C0 is substantially constant. 4. Claims 1 to 3, wherein the positive dielectric anisotropic liquid crystal is an encapsulated nematic liquid crystal. The device described in any of the above. 5. An electrical device, (a) Each is made of positive dielectric anisotropic liquid crystal, and has a capacitance below the threshold voltage. Liquid crystal display with capacitance C1 and capacitance C2 above the saturation voltage (b) connected in series with the display at the end of said array; and inequality: C0<C2/n [where n is the number of displays in the array. ] Capacitance that satisfies A device comprising a capacitor having a sC0. 6. 6. The apparatus of claim 5, wherein C0 is substantially constant. 7. Claim 5 or 5, wherein the positive dielectric anisotropic liquid crystal is an encapsulated nematic liquid crystal. The device according to item 6. 8. An electrical circuit, (a) Consists of a positive dielectric anisotropic liquid crystal, with capacitances C1 and C1 below the threshold voltage. a liquid crystal display having a capacitance C2 above the saturation voltage; (b) a capacitor in series with the display; and (c) the display. A voltage lower than the withstand voltage of the display is applied across the combination of the display and the capacitor. A circuit comprising means for applying pressure. 9. Claim 8, wherein the capacitor has a substantially constant capacitance. The circuit described. 10. Claim 9, wherein the substantially constant capacitance is less than or equal to C2. circuit. 11. Claims in which the substantially constant capacitance is present between C1 and C2 The circuit described in box 9. 12. Claim 1 further comprising at least one additional liquid crystal display. The circuit described in item 8. 13. The one or more additional liquid crystal display elements are 13. The circuit according to claim 12, which is connected in series with the circuit. 14. The means must be a power source having an output voltage equal to or lower than the withstand voltage of the display. The circuit according to claim 8. 15. The means includes a power source and a power supply having an output voltage higher than the withstand voltage of the display. 9. The circuit according to claim 8, which is pressure lowering means. 16. Claims wherein the voltage drop means is a capacitor connected in series with the power supply. 15. The circuit according to item 15.