JPS62200325A - Ferroelectric liquid crystal element - Google Patents

Abstract

PURPOSE:To prevent the destruction of protective film to improve the reliability by specifying the hardness of the protective film on a color filter. CONSTITUTION:On a ferroelectric liquid crystal element 1, a ferroelectric liquid crystal 4 an ball-shaped bead specers 9 are held between a pair of parallel substrates 2 and 3 provided with transparent electrodes 5 and 6, and a color filter 11 and a protective film 10 and provided between at least one electrode 5 and one substrate 2. This film 10 on the filter 11 consists of a transparent resin or a transparent inorganic compound and is formed with >=HB pencil harness (JIS K 5401). Oriented films 7 and 8 are provided between electrodes 5 and 6 and the liquid crystal 4. Since the destruction of the film due to spacers 9 is prevented in this constitution, the element 1 of high reliability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ferroelectric liquid crystal element suitable for color displays, particularly color televisions.

In this specification, pencil hardness refers to JIS K 5401
Refers to the hardness measured using a "pencil scratch tester for paint films" specified in .

[Summary of the Disclosure] This specification and drawings describe a ferroelectric liquid crystal element used in a liquid crystal display element using beads as a spacer, a liquid crystal-light shutter array, etc. By forming the protective film, destruction of the protective film can be prevented and a highly reliable ferroelectric liquid crystal element can be obtained.

[Prior Art] In a liquid crystal television panel using a conventional active matrix driving method, thin film transistors (TPTs) are arranged in a matrix for each pixel, and a gate-on pulse is applied to the TPTs to bring the source and drain into a conductive state. At this time, a video image signal is applied from the source and stored in the capacitor, and a liquid crystal (for example, twisted nematic-TN liquid crystal) is driven in response to this stored image signal, and a color filter layer provided for each pixel is driven. Color displays were produced by optical switching.

However, in active matrix drive type television panels using such TN liquid crystals, the TPT used is
Because TPT has a complicated structure, it requires a large number of structural steps and high manufacturing costs. There are problems in that it is difficult to form a film over a long period of time.

On the other hand, a passive matrix drive type display panel using TN liquid crystal is known as a device that can be manufactured at low manufacturing cost, but in this display panel, as the number of scanning lines (N) increases, one screen (one frame) 1 while scanning
The time during which an effective electric field is applied to one selected point (duty ratio) decreases at a rate of 1/H, which causes crosstalk and has drawbacks such as not providing a high-contrast image. Moreover, when the duty ratio becomes low, it becomes difficult to control the gradation of each pixel by voltage modulation, making it unsuitable for display panels with a high density of wiring, especially liquid crystal television panels.

In order to solve the fundamental problems of conventional TN liquid crystals, a ferroelectric liquid crystal element having bistability has been proposed, such as in US Pat. No. 4,387,924 by Clark and Lagerwal et al.

The above-mentioned bistable ferroelectric liquid crystal element needs to be designed with an extremely thin cell thickness of about 175 to 1/1O of that of a conventional TN type liquid crystal element, and the cell thickness is reduced by 10% over the entire surface. Since it is necessary to control the parallelism within the following tolerance range, consideration is generally given to keeping the parallelism of the parallel substrates as constant as possible by using alumina beads as spacers and further reducing the pressure inside the cell.

[Problems to be Solved by the Invention] When color display is performed by forming a color filter on a substrate, a protective film is uniformly formed on the surface of the color filter. However, when the protective film used in conventional nematic type elements is used in ferroelectric liquid crystal elements, problems arise due to differences in internal pressure. That is, as shown in FIG. 5, the bead spacer 57 that maintains the cell thickness is strongly pressed against the substrate in point contact due to the pressure applied to the cell, so the conventional protective film is insufficiently hard, and the bead spacer 57 is not protective. In some cases, the liquid broke through the film 53 and reached the color filter 51. As a result,
Orientation defects in the liquid crystal phase occur in the destroyed area, and furthermore, the ferroelectric liquid crystal soaks into the destroyed area and comes into contact with the dye, which gradually contaminates the liquid crystal and significantly lowers its resistance value, causing the element to deteriorate. The disadvantage was that the drive became unstable.

In particular, it has been found that if a ferroelectric liquid crystal element in which the color filter 51 has been destroyed is used for a long period of time, a problem arises in that a normal color display cannot be performed.

FIG. 6(a) shows a driving waveform applied to a pixel of one ferroelectric liquid crystal, and FIG. 6(b) shows a voltage waveform applied to the liquid crystal itself in real time. That is, when a writing pulse of Voo is applied to the ferroelectric liquid crystal from between the above-mentioned crossed electrodes, the voltage waveform substantially applied to the ferroelectric liquid crystal is as shown in FIG. 6(b) when the pulse is applied. vO causes a voltage drop by ΔVo at the rate of time constant π = RC (R: resistance of the ferroelectric liquid crystal, C: capacitance of the ferroelectric liquid crystal), and this voltage drop ΔVO is caused by the resistance R of the ferroelectric liquid crystal. The smaller the value, the larger it becomes, and -ΔVo of opposite polarity is applied to the ferroelectric liquid crystal at the time of pulse switching (at the falling edge of the pulse). If this 1-ΔVo I is larger than the inversion threshold voltage 1-Vthl, black writing, which is opposite to white writing, is activated, for example. This is caused by an electric field (-ΔVn) in the opposite direction due to discharge from the capacitance of a dielectric layer such as an alignment control film connected in series with the ferroelectric liquid crystal at the falling edge of the pulse.
This is caused by the occurrence of

By the way, the liquid crystal element for color display mentioned above is
The protective film of the color filter is destroyed by the suppression of the bead spacer, and as a result, the dye in the color filter layer is eluted into the ferroelectric liquid crystal inside the cell, and if such a liquid crystal element is used for a long time, the strength inside the cell will be There is a problem in that the resistance R of the dielectric liquid crystal decreases over time, and eventually the value of the above-mentioned reverse electric field -Δ■o exceeds the inversion threshold voltage, and the desired optical switching drive no longer operates.

In addition, when applying the row sequential writing method to a ferroelectric liquid crystal element, for example, the first
A pulse is applied to form a first display state island based on the first alignment state of the ferroelectric liquid crystal at a phase tl, and a pulse is applied to the selected pixel at a phase t2, which is a first-order second phase. There is a method of applying a pulse that inverts the display state to a second display state based on the second alignment state of the ferroelectric liquid crystal.

In this method, at phase t2, as shown in FIG. 7(a), a pulse with the opposite polarity to the pulse applied at phase t1 is applied to the pixel that maintains the first display state at a voltage below the threshold voltage. Become.

In this manner, in the case of the row sequential writing method, it is necessary that the display state written in one phase t1 be maintained without being reversed in phase t2. Therefore, a voltage exceeding the inversion threshold voltage should not be applied at phase t2, but when switching the pulse polarity from phase tl to phase t2, the ferroelectric liquid crystal will have the voltage shown in Figure 7(b). Similarly = (aV6 +ΔVo)
:(a is a < l Vth l / l Von l
; Vth is the threshold voltage of the ferroelectric liquid crystal] A voltage of : is substantially applied, and this -(a V 6
+ΔVO) is larger than the inversion threshold voltage, the pixels that should maintain the first display state are inverted to the second display state at phase t2, making it impossible to form the desired display. was there.

The purpose of the present invention is to prevent the occurrence of the above-mentioned alignment defects and the decrease in the resistance value of the liquid crystal, and to provide a highly reliable ferroelectric liquid crystal device that can fully utilize the high-speed response and memory effect characteristics inherent in the ferroelectric liquid crystal element. An object of the present invention is to provide a ferroelectric liquid crystal element.

[Means for Solving the Problem] and [Operation] That is, the present invention provides a ferroelectric liquid crystal element having a pair of parallel substrates, and a ferroelectric liquid crystal and a bead spacer arranged between the pair of parallel substrates. A ferroelectric liquid crystal device, characterized in that a color filter is provided on at least one of the pair of parallel substrates, and a protective film having a pencil hardness of H8 or higher is formed on the color filter. It has the following characteristics. In this way, by forming the protective film on the color filter to have a hardness of pencil hardness H8 or higher, it is possible to prevent the film from being destroyed by the bead spacers.

[Example] FIG. 3 schematically depicts an example of a cell for explaining the operation of a ferroelectric liquid crystal. 31 and 31' are In20
2, 5n02 or ITO (Indium-Tin
It is a substrate (glass plate) coated with a transparent electrode made of a thin film such as -Owide), between which a 5taC-phase or Sm
H-phase liquid crystal is sealed. A thick line 33 represents a liquid crystal molecule, and this liquid crystal molecule 33 has a dipole moment (P, ) 34 in a direction perpendicular to the molecule. When a voltage higher than a certain threshold is applied between the electrodes on the substrates 31 and 31', the helical structure of the liquid crystal molecules 33 is unraveled, and the liquid crystal molecules 33 are turned so that all the dipole moments (P, ) 34 are oriented in the direction of the electric field. The orientation direction can be changed. The liquid crystal molecules 33 have an elongated shape and exhibit refractive index anisotropy in the long axis direction and the short axis direction. Therefore, for example, if crossed Nicol polarizers are placed above and below the glass surface, the polarity of the applied voltage will change depending on the polarity of voltage application. It is easily understood that this results in a liquid crystal optical modulation element whose optical properties change.

The liquid crystal cell preferably used in the liquid crystal element of the present invention can be made sufficiently thin (for example, 10p or less).As the liquid crystal layer becomes thinner, the electric field increases as shown in FIG. Even when no voltage is applied, the helical structure of the liquid crystal molecules unwinds and becomes a non-helical structure, and the dipole moment P or P' is directed upward (34) or downward (34).
34'). In a cell like this,
As shown in Figure 4, electric fields E with different polarities above a certain threshold value
or when E' is applied by the voltage applying means 38 and 36', the dipole moment changes its direction upward 34 or downward 34' in response to the electric field vector of the electric field E or E',
Accordingly, the liquid crystal molecules are aligned in either the first stable state 35 or the second stable state 35'.

As mentioned above, there are two advantages to using such ferroelectricity as a liquid crystal element. The first is that the response speed is extremely fast, and the second is that the alignment of liquid crystal molecules has bistability. To further explain the second point with reference to FIG. 4, for example, when an electric field E is applied, liquid crystal molecules
This state is stable even when the electric field is turned off. Also, when applying an electric field E' in the opposite direction,
The liquid crystal molecules are oriented to a second stable state 35' and change their orientation, but remain in this state even after the electric field is removed. Further, as long as the applied electric field E does not exceed a certain threshold value, each orientation state is maintained. In order to effectively realize such fast response speed and bistability, it is preferable that the cell be as thin as possible, and in order for this ferroelectric liquid crystal element to exhibit predetermined driving characteristics, It is necessary that the ferroelectric liquid crystal placed between a pair of parallel substrates be in a molecular arrangement state that effectively converts between the two stable states, regardless of the applied state of the electric field. be. For example, in a ferroelectric liquid crystal having a chiral smectic phase, a layer of liquid crystal molecules in the chiral smectic phase is perpendicular to the substrate surface, thus forming a region (monodomain) in which the liquid crystal molecular axes are aligned almost parallel to the substrate surface. It is necessary to Therefore, it is desirable for the cell to have a highly parallel substrate and a uniform substrate surface.

Means for solving the above problems will be explained using FIG. 1 corresponding to an embodiment.

A ferroelectric liquid crystal 4 is sandwiched between a pair of parallel substrates 2.3 on which transparent electrodes 5 and 6 are formed, and a color filter 11 (R) is placed between at least one of the transparent electrodes and the substrates.

G, B), a protective film 1 having a pencil hardness of H8 or higher made of a dye and a transparent resin or a transparent inorganic compound is provided on a color filter 11 of each pixel.
0 and a spherical bead 9 is sandwiched between the substrates as a spacer.

Particularly suitable liquid crystal materials for use in the present invention are liquid crystals with bistability and ferroelectricity, specifically chiral smectic C phase (S+sC
” phase), H phase (SmH, 1 phase (Sat umbrella phase), J phase (
It is possible to use a liquid crystal of a phase K (SmJ small phase), a K phase (SmK'' phase), a G phase (SmG medium phase), or an F phase (SmF small phase).

Regarding this ferroelectric liquid crystal, please refer to “Le Journal de Physique Rutile”.
PHYSIQUE LETTERS") 1975, 3El (L-89), "Ferroelectric
Liquid Crystals J (rFerroelect
ricliquid CrystalsJ) ; “Applied Physics Letters (App I i
edphysics Letters”) 1980
Year, No. 3B (11), “Submicro Second Bistiple Electro-Optic Switching in Liquid Crystals”
o 5econdBistableElectroo
ptic Switching in LiquidC
rystaltJ) ; "Solid State Physics" 1981, 1
B (141), "Liquid Crystal", etc., and the ferroelectric liquid crystal disclosed therein can be used in the present invention.

Specific examples of ferroelectric liquid crystal compounds include decyloxybenzylidene-p'-amino-2-methylbutylcinnamate (DOBAMBG) and hexyloxybenzylidene-p'-amino-2-methylbutylcinnamate (DOBAMBG).
p'-amino-2-chloropropylcinnamate (HO
BACPC), 4-o-(2-methyl)-butylresolsiliten-4'-octylaniline (MBRA8).

When constructing an element using these materials, the element can be supported by a block with a heater embedded, etc., as necessary, in order to maintain the temperature at which the liquid crystal compound enters the chiral smectic phase. .

Materials for the alignment control film used in the present invention include, for example, polyvinyl alcohol, polyimide, polyamideimide, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin, and Yuria resin. , resins such as acrylic resin, photosensitive polyimide, cyclized rubber photoresist, phenol novolak photoresist, or electron beam photoresist [polymethyl methacrylate, epoxidized-1,4-polybutadiene, etc.]. can be formed.

The color filter 11 can be formed by coloring a mordant such as polyvinyl alcohol or cellulose resin with a dye. Dyes used in this case include cyanine dyes, merocyanine dyes, azulenium dyes, naphthoquinone dyes, naphthoquinone dyes, phenol dyes, disazo dyes, trisazo dyes,
Tetrazo dyes and the like can be used.

The color filter 11 used in the present invention may be formed by coating various organic pigments by vapor deposition. Examples of the organic pigments used in this case include copper phthalocyanine pigments, lead phthalocyanine pigments, and perylene pigments. , indigo pigments, thioindigo pigments, disazo pigments,
Trisazo pigments, tetrazo pigments, anthraquinone pigments, quinacridone pigments, isoindolinone pigments,
Dioxazine pigments, perinone pigments, pyrocholine pigments, fluorobin pigments, quinophthalone pigments, and the like can be used.

In another preferred embodiment of the present invention, colored polyimide, colored polyamide, colored polyamideimide, colored ester imide, or colored polyester can be used as the color filter 11.

In particular, since polyamide (6-nylon, 86-nylon or copolymerized nylon) and polyester are soluble in various organic solvents, various organic pigments can be mixed therein. In addition, as a method for coloring polyimide, polyamideimide, and polyesterimide, a dispersant (hydroxyl group, carboxyl group, sulfonic acid group, carbonamide group, sulfonamide group, etc.) as a substituent is added to a polyamic acid solution, which is the precursor thereof. A method of dispersing organic pigments together with azo dyes, phthalocyanine dyes, triphenylmethane dyes, etc.) can be used. These colored films have extremely good adhesion to the retaining W1 film IO, and good results can be obtained.

A protective film made of transparent insulating resin used in the present invention;
Examples of alo include rubber photoresists, thermosetting acrylic resin polyimide, polyparaxylylene (trade name: Parylene, Union Carbide), polyethylene, polystyrene, polycarbonate, and the like. As a coating method for these, a spinner coating method can be used. In addition, an M-retaining film made of a transparent insulating inorganic compound
As O, 5iQ2. AhOz, Tf02. Z
Examples include rO2, Mgh, SjO, and the like.

When the above-mentioned protective film is formed to have a hardness of pencil hardness HB or higher, destruction of the film by the bead spacer can be prevented. Therefore, since the unevenness that causes alignment defects on the substrate surface is removed, the liquid crystal phase region of the liquid crystal layer sandwiched between the flat substrates gradually expands and becomes uniform during the cooling process during which the liquid crystal phase transitions from the isotonic phase to the liquid crystal phase. A monodomain liquid crystal phase is formed.

For example, the above-mentioned DOBA exhibiting a ferroelectric liquid crystal phase as a liquid crystal.
Taking MBC as an example, when cooling slowly from the Tokiyoshi phase of DOBAMBC, it undergoes a phase transition to a smectic A phase (S layer^ phase) at about 115°C. At this time, if the substrate is subjected to alignment treatment such as rubbing or oblique deposition of Si02, monodomains are formed in which the molecular axes of liquid crystal molecules are parallel to the substrate and oriented in one direction. Furthermore, as the cooling progresses, it will reach approximately 90 to 75 degrees Celsius depending on the thickness of the liquid crystal layer.
The chiral smectic C phase (Sac
In addition, when the thickness of the liquid crystal layer is about 2 mm or less, the helix of the Sac phase is unraveled, and at least
A ferroelectric liquid crystal having a stable state of f and a second stable state can be obtained.

The film thickness of this protective film 10 is 5000A or less, preferably 100A to 5000A, particularly 500A to 300A.
0A is suitable.

In addition, in the case of the capacitance formed by this protective film 10, 5
．． By setting it to 5 x 103 PF/cm2 or more, the above-mentioned inversion phenomenon can be more effectively prevented. Its preferred capacity is 5.5 X 103P
F/c+w2~3. 9. In particular, maintaining sufficient insulation in the range of OX 105PF/cm2. OX103P
F/crm2 to 5.5 x 104PF/crm2 is suitable.

As described above, by setting the hardness of the protective film 10 used in the present invention to be 0.8 or higher, the destruction of the protective film 10 caused by the suppression of beads is prevented, and therefore the dyes and pigments in the color filter are transferred to the ferroelectric liquid crystal 4. Since it does not dissolve in the water, problems caused by a decrease in resistance do not occur.

Figure 1 shows the basics of the ferroelectric liquid crystal element according to the present invention +tlI
It is a sectional view showing J&. In FIG. 1, a ferroelectric liquid crystal element 1 has substrates 2 and 3 made of transparent plates such as glass plates or plastic plates, and an encapsulated liquid crystal 4 is placed between them.
is being held. Striped transparent electrodes 5 and 6 forming a matrix electrode structure are arranged on each of the substrates 2 and 3, and alignment films 7 and 8 are formed on each of the transparent electrodes.

The color filter 11 made of R, G, and H pigments is
It is formed of a pigment, a pigment and a transparent Φ resin, or a pigment and a transparent inorganic compound so that the film thickness is approximately equal. On the other hand, a transparent protective film 10 is formed between the color filter 11 and the transparent electrode 5.

In the substrate with the above configuration, the color filters 11 are formed to have almost the same thickness, so even if a protective film, a transparent electrode, and an alignment film are sequentially formed on the pixels, the substrate surface can be kept almost flat. .

In the present invention, the level difference on the surface of the substrate on the color filter side can be made to be 100 OA or less by the above-mentioned planarization, but it is preferably 500 OA or less. A liquid crystal element that does not use a flattening layer will have alignment defects of edge lines.

Although the alignment film 7 depends on the film thickness of the ferroelectric liquid crystal,
Generally 10A-1p, preferably 100A-3000
Set to range A. The thickness of the protective film 10 can determine the thickness of the ferroelectric liquid crystal 4, so it varies depending on the type of liquid crystal material, the required response speed, etc., but is generally 0.2 ~20JL, preferably 0.5
It is set within the range of 10g. Further, the hardness of the film is set to be 08 or more on the pencil hardness scale as described above.

Examples of the present invention will be described in more detail below.

FIGS. 2(a) to 2(f) are diagrams showing the process of forming three color pixels of R, G, and B. First, Corning's 170
59 Positive resist (product name, 0
FPR77, manufactured by Tokyo Ohka) using a spinner, OI
A resist layer 22 was provided (second resist layer 22).
(See Figure C) Next, this is exposed using a predetermined pattern mask 23 (see Figure 2).

Or'r'R7? A lift-off pattern 22a having a predetermined stripe shape was formed by developing with a series developer (see FIG. 2C).

Next, the entire pattern-forming surface of the glass substrate 21 was exposed to light, and resist residue other than unnecessary pattern areas was removed from the glass substrate 21 by oxygen plasma ashing.

In this way, the glass substrate 22 on which the lift-off pattern 22a has been formed is placed at a predetermined position in the vacuum evaporation apparatus, and nickel phthalocyanine is applied as a blue pigment for evaporation to one of the two molybdenum ports as evaporation sources. Parylene (manufactured by Union Carbide) was put into the other port as a resin, and the evaporation temperature of the former was adjusted to 470°C and the temperature of the latter was adjusted to 250°C.
A colored layer 54 was formed by vapor deposition on the lift-off pattern formation surface of the 0OA2Jli board 21 (see FIG. 2C).

The substrate 21 on which the lift-off pattern 22a and the colored layer 24 are formed is immersed and stirred in a developer exclusively for the 0FPR77 series for 5 minutes, and the colored layer 24a deposited on this pattern is removed from the substrate together with the resist pattern 22a. A striped filter was prepared (see Figure 2C).

On the other hand, the green and red striped filters are shown in Figure 2 (
It is obtained by repeating the steps a) to (e).

Namal phthalocyanine was used as a green vapor deposition pigment at 55%.
A line layer was formed by 0OA vapor deposition.

Next, 55% of anthraquinone was added as a red dye for vapor deposition.
A red layer was formed by 0OA vapor deposition.

In the above manner, B is obtained as shown in FIG. 2(f).

It was possible to form color filters with approximately the same thickness for both G and R.

Example 1 Next, the protection Il! of FIG. ! Hitachi Chemical's H as IIO
L-1100 (polyether amide imide) was applied using a spinner and further heated and cured at 100° C. for 30 minutes to give a film thickness of 1 layer. The hardness of the protective film 10 at this time was 5H on a pencil hardness scale.

Next, as shown in the IF diagram, an ITO film was formed to a thickness of 50 OA by sputtering, and then patterned to form a transparent electrode 5. On top of this, as an alignment film 7, a polyimide forming solution (Hitachi Chemical rPIQJ) was applied for 30 minutes.
A 200 OA polyimide film was formed by applying a 00 rpm layer using a rotating spinner and heating at 150° C. for 30 minutes. Thereafter, the surface of this polyimide film was subjected to a rubbing treatment.

Between the substrate 2 on the color filter side thus formed and the opposing substrate 3, alumina beads with an average particle size of IJLi are scattered as spacers to maintain the cell thickness, and both plates are bonded together to form a cell. The following ferroelectric liquid crystal was injected and sealed to obtain a liquid crystal element. When this liquid crystal element was observed using a crossed Nicol polarizing microscope, it was confirmed that the film was not destroyed by the bead spacer 9 and that the liquid crystal molecules inside had no alignment defects.

Example 2 The protective film 10 was formed of a thermosetting resin made of an acrylic polymer, and the other configurations were exactly the same as in Example 1.

The hardness of the protective film 10 at this time was a pencil hardness of HE.

When the device having the above structure was observed using a crossed Nicol polarizing microscope, it was found that, as in Example 1, there was no destruction of the protective film due to the bead spacers, and an element free of orientation defects could be obtained.

Comparative Example The protective film 10 was formed of polyvinyl alcohol (PVA), and the other configurations were completely the same as those of the previous example. The hardness of the protective film 10 at this time was 2B on the pencil hardness scale.

When the device having the above structure was observed using a crossed Nicol polarizing microscope, defects were observed, and significant alignment defects in the liquid crystal phase were observed in the defective portions.

The three types of liquid crystal cells mentioned above were heated at a temperature of 40°C and a relative humidity of 85%.
The resistance of each liquid crystal was measured after being left for 8 B hours under the following conditions. The results are shown below (Table 1).

Table 1 When these three types of liquid crystal cells were driven, the driving of the liquid crystal cells of Examples 1 and 2 was stable, but the driving of the liquid crystal cell of Comparative Example was unstable.

The above-mentioned resistance (Ω・cm) can be calculated by using the circuit shown in Figure 8.
By applying a rectangular pulse using the frequency method, R is calculated from the following formula.
It can be measured by finding LC(Ω·cs+). In this case, f 1 = 32Hz,
f 2 = 84 Hz, V = to volts.

f: frequency of square wave ■c: Current value of capacitive component IR: Current value of R component CLC: Liquid crystal capacity Rtcs liquid crystal resistance (Ω) CLC: RLC3/d d: Liquid crystal film thickness (cell gap) S: Electrode area Change f.

[Effects of the Invention] As explained above, according to the present invention, by forming a protective film having a pencil hardness of 88 or more on the color filter, film destruction due to point contact of bead spacers is eliminated. It is possible to prevent a decrease in the resistance value of the liquid crystal caused by alignment defects or film destruction. Therefore, it is possible to provide a highly reliable ferroelectric liquid crystal element that can exhibit the characteristics of a ferroelectric liquid crystal.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the basic structure of a ferroelectric liquid crystal element according to the present invention, FIGS. 2(a) to (f) are views showing the process of forming color pixels, and FIGS. 3 and 4 are views according to the present invention. FIG. 5 is a cross-sectional view of the broken part, FIGS. 6(a) and (b) are explanatory diagrams showing voltage waveforms during writing, and FIG. 7 is a schematic perspective view of a ferroelectric liquid crystal used in (a) and (b) are explanatory diagrams showing voltage waveforms during another write operation, and FIG. 8 is a diagram of a resistance measurement circuit used in this embodiment. 1... Ferroelectric liquid crystal element, 2.3... Substrate, 4...
・Ferroelectric liquid crystal, 5, 6...transparent electrode, 7.8...
Alignment film, 9... Bead spacer, 10... W retaining film, 11... Color filter.

Claims (1)

[Claims] In a ferroelectric liquid crystal element having a pair of parallel substrates, and a ferroelectric liquid crystal and a bead spacer arranged between the pair of parallel substrates, at least one of the pair of parallel substrates is provided with a color filter. Along with being there,
A protective film with a pencil hardness of HB or higher (however, pencil hardness refers to the hardness measured by a "pencil scratching tester for paint films" specified in JIS K 5401) is formed on the color filter. Ferroelectric liquid crystal element with special features.