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JPH01175400

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DESCRIPTION JPH01175400
[0001]
[Industrial field of application] The present invention relates to an electric field applied to a liquid
crystal layer (corresponding to a liquid crystal acoustic element that vibrates to generate a sound,
and can be used as a sound wave generator for thin speakers etc.) Are suitable for panel
illumination and the like. 2. Description of the Related Art Conventionally, a liquid crystal display
device can be made thin and light, and is widely used in portable televisions and the like. In order
to more effectively utilize the thinness and lightness of the liquid crystal in such portable
televisions and the like, it is essential to miniaturize and lighten the other components. However,
since a magnetic speaker is exclusively used for audio reproduction, there is a limit to reducing
the size and weight, and in order to miniaturize it, the integrated built-in speaker is excluded
without exception, and an earphone etc. is exclusively used. Means are adopted. To solve such
problems, it is known that when an alternating voltage is applied to a ferroelectric liquid crystal,
the liquid crystal can generate an acoustic wave corresponding to the voltage E) J L and the
voltage. It has been proposed to use a liquid crystal acoustic element using a ferroelectric liquid
crystal (see JP-A-62-47300). [Problems to be Solved by the Invention] However, a liquid crystal
of a low molecular weight such as OBAMBC (11-decyloxybenzylidene p'amino 2 methyl butyl
cinnamate) is generally used as a ferroelectric liquid crystal in the prior art. The process of
holding between the pair of electrodes takes time and requires precise control at the time of
manufacture. In particular, alignment processing which is essential for providing an image
display function is difficult, and it is difficult to manufacture a large-area product. In addition,
when a liquid crystal acoustic element is formed using a low molecular weight ferroelectric liquid
crystal, the liquid crystal phase has poor flexibility, is weak to shock, is easily broken by bending,
and can not be used as a liquid crystal element using a flexible substrate. . Furthermore, since it
is not flexible, the utilization efficiency of vibration at the time of sound generation is low, and
there is a problem that it is difficult to obtain a practical sound pressure level or a sufficient
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reproduction bandwidth. An object of the present invention is to provide a liquid crystal acoustic
element which has high acoustic efficiency, can simultaneously generate sound and display an
image, can be easily mass-produced, can be formed into a large area, and can be bent. [Means for
Solving the Problems] The present invention is a liquid crystal acoustic element in which a liquid
crystal layer disposed between a pair of electrodes is formed of a ferroelectric polymer liquid
crystal having 11,000 or more molecules. The ferroelectric polymer liquid crystal to be used in
the present invention will be described in detail later, but as an example, polyacrylate type,
polyether type, polysiloxane type, polyester type, copolymers containing repeating units of these
respective types , By others.
[Operation] In such a configuration, when a direct current or an alternating voltage of the old 1z
frequency is applied between the pair of electrodes, the ferroelectric polymer liquid crystal
constituting the liquid crystal layer according to the change of the electric field between both
electrodes Each molecule vibrates, and a plane wave is generated by the vibration of the
component in the plane orthogonal direction of the liquid crystal layer, thereby generating a
sound wave corresponding to the frequency of the applied voltage. Further, in the present
invention, since the ferroelectric polymer liquid crystal is used in the liquid crystal layer of the
liquid crystal acoustic element, the film forming property is good, the structure is simple, the
productivity is high, and the enlargement is easy, It is possible to realize the display function at
the same time because the coating can be easily oriented. Embodiments of the present invention
will be described below with reference to the drawings. 1 and 2 show an embodiment of a liquid
crystal acoustic device 10 according to the present invention, which is configured to
simultaneously perform basic sound generation and image display. It is. The liquid crystal
acoustic element 10 is provided with a transparent substrate 11 made of glass or flexible
polyethylene terephthalate, polymethyl methacrylate, polycarbonate and other plastics as a
support layer, and on this substrate 11, an oxidation called NES film is made. Metal oxide film
such as indium oxide (r,, 03) film mixed with tin oxide called tin (S70 □) film or ITO film, or gold
(Au), aluminum (AI), titanium (T,) A stripe-shaped transparent electrode 12 made of a metal thin
film such as, for example, is provided. A liquid crystal layer 13 is formed on the transparent
electrode 12 after the ferroelectric polymer liquid crystal is sufficiently aligned at a thickness of
5 μm or less by a drawing method or a coating method. On the liquid crystal layer 13, a
transparent substrate 15 of the same material as that described above and in contact with the
transparent substrate 15 of the same material as the substrate 11 having the stripe-shaped
transparent electrode 14 is adhered. The liquid crystal acoustic element 10 is formed. Here, after
forming a film of the above-mentioned material on the substrate 11.15 by evaporation or the
like, each of the electrodes 12.14 is formed into a plurality of stripes by etching or the like, and
the stripes of the opposing electrodes 12.14 overlap each other. A plurality of points which are
arranged in a grid shape and each stripe crosses each other form a matrix corresponding to a
plurality of pixels in image display. Further, on the outer side of each of the transparent
substrates 11.15, in order to realize image display, the linear polarizers 16.17 which interrupt
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transmitted light by the change of the optical state of the liquid crystal layer 13 sandwich the
liquid crystal JW13. It is arranged opposite to.
In such a configuration, the illumination light 20 is irradiated from above through the polarizing
plate 17 and the voltage as shown in FIG. 3 is applied between the transparent electrodes 12.14
to make the liquid crystal acoustic element 10 acoustic. The generation and image display are
performed simultaneously. First, when a display signal voltage of + 1 is applied between the
electrodes 12.14 corresponding to predetermined pixels at time T in FIG. 3, the ferroelectric
polymer liquid crystal constituting the liquid crystal layer 13 has predetermined optical
characteristics. It is maintained in a static state, for example, a state in which light is allowed to
pass, and the liquid crystal layer 13 at that position passes the transmitted light 2OA to the
polarizing plate 16 side as shown in FIG. As a result, a predetermined image is displayed on the
liquid crystal acoustic element 10. Here, as shown at time T2 to T in FIG. 3, when an audio signal
voltage of a predetermined audio frequency is applied in addition to the display signal voltage,
the liquid crystal layer 13 is induced to vibrate and the liquid crystal acoustic element 10
Generate sounds in the audible area. At this time, if the amplitude 2 of the audio signal voltage is
set to 1 or less, the existing display signal voltage here does not cancel + 1 and the liquid crystal
layer 13 vibrates in the predetermined optical state. The acoustic element 10 simultaneously
generates sound such as voice while displaying the predetermined image. Further, as shown at
time T in FIG. 3, when the display signal voltage is changed to -VI, the optical state of the liquid
crystal layer 13 is inverted along with the ferroelectric inversion of the ferroelectric polymer
liquid crystal. Block the transmitted light 2OA. For this reason, the distribution for each pixel of
the transmitted light 2OA of FIG. 2 changes, and the image displayed on the liquid crystal
acoustic element 10 changes. Therefore, according to the liquid crystal acoustic element 10,
generation of sound and display of an image can be simultaneously performed by the display
signal voltage (1) and the audio signal voltage (2). If the display signal voltage {circle over (1)} is
changed while the audio signal voltage v2 is applied, it is also possible to change the display
image in the sound generation state. In addition, although the liquid crystal layer 13 can
generate sound if it has a thickness of 100 μm or less, by setting it to 5 μm or less, it is possible
to generate sound as well as sound, and its thickness can be several μm to realize a bistable
state. It may be possible. Furthermore, the alignment process is not required for the ferroelectric
polymer liquid crystal of the liquid crystal layer 13 when only sound generation is performed,
but the alignment process is performed for the ferroelectric polymer liquid crystal when image
display is performed simultaneously with the sound generation. It is necessary to apply the
rubbing method, the shearing method, the drawing method and the coating method as the
alignment method, and in the case of using the ferroelectric polymer liquid crystal among them,
the coating method is easy.
Further, the electrodes 12.14 are not limited to those in which both are formed into a plurality of
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stripes etc. to form a matrix, and when used for a bar graph etc., one of them is plural and the
other is an arrangement of the plural electrodes. A single common electrode may be provided in
the above-mentioned range, and the electrodes 12.14 may be formed into thin films one by one if
image display is not required. Furthermore, the polarizing plates 16.17 may be arranged in the
cross nicol state or in the parallel nicol state, or the polarizing plate 16.17 may be omitted if
image display is not performed. In this case, it is not necessary to make the electrode 12.14 or
the substrate 11.15 transparent. Next, the liquid crystal used in the present invention will be
described. The ferroelectric polymer liquid crystal to be used in the present invention is not
particularly limited and various ones can be used, but usually, a polymer compound having
mesogen in the side chain via a spacer can be suitably used. The side chain type polymer liquid
crystal is composed of three parts of a polymer main chain, mesogen and a spacer, and for
example, one represented by the following single vessel formula (1) can be mentioned. -+ Eh-+ E
') b (1) wherein,-(E +-r-+ E') is a polymer main, D is a spacer, and M is mesogen. bは、0であって
もよい。 When b is not O, the unit of (E-D-M ′ ′) and the unit of (E ′) in the formula are
linked alternately, whether linked in a block or randomly. It may be As main chains, main chains
of various polymers can be used, and as preferable main chains, polyacrylates, polysiloxanes,
polyethers, polyesters, polymethacrylates and the like can be mentioned. Although various things
can be used as the spacer D, For example, the thing represented by following (2) Formula can be
mentioned as a suitable thing. -(-C00-> CHz) r (2) However, in formula (2), m represents 0 or 1, n
represents the integer of 1-30. Although various things can be used as the mesogen M, For
example, what is represented by following (3) Formula can be used suitably. → Z h-RI (3) where
(2) is O or 1 and Z is 0 (oxygen atom) or -COO- (ester bond), T is shown in the following (4)
Those represented by the following formulas can be suitably used.
However, in each formula of the above (4), X represents, for example, -COO-, -〇CO-, R2
represents, for example, -COORz, -0 CORs, -0 Rs, -CORs, Rs, and this R1 is not It is a C4-10
chained or branched alkyl group containing one or more homogeneous carbons, a haloalkyl
group or a cyanoalkyl group. Among these polymer liquid crystals, ferroelectric polymer liquid
crystals are preferable in terms of electric field response speed, contrast, etc., and in particular,
ferroelectric polymer liquid crystals having a chiral smectic C phase (S, C “phase”) are
preferable. . Examples of such a ferroelectric liquid crystal having a chiral smectic C phase
include the following (1) to ([]) polymer liquid crystals. Those high molecular liquid crystals of (1)
to (V) usually have a chiral smectic C phase in a temperature range from room temperature to
about 150 ° C., and are extremely excellent in response speed, contrast and film formability. It
is. (+) Polyacrylate Polymer Liquid Crystals (such as those filed by the present applicant as
Japanese Patent Application Nos. 61-305251 and 62-106353) Polyacrylate polymers having
repeating units of the following general formula The copolymer (cl, -CH ← C00 → CHz + -TZ-R +,
wherein k is an integer from 1 to 30, preferably 4; X is -coo- or -oco-; and Rx is -COOR *, -0COR3,
-0Rs, or -R1, where R3 can be where R4, Rs is-cttz, CIJ, F or C1, preferably -CH3, and g and h are
integers from 0 to 10, q is O or 1, and C ′ ′ is an asymmetric carbon atom. However, when R3
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is -CHI, h is not 0, and -CHzCH-CJ + s can be mentioned as particularly preferable one as R1. (II)
Polyether-Based Polymer Liquid Crystal (The one filed by the present applicant as Japanese
Patent Application No. 61-309466, etc.) Polyether-based polymer having a repeating unit
consisting of the following general formula and copolymer thereof: R, has the same meaning as in
the polyacrylate system. (III) Polysiloxane-Based Polymer Liquid Crystal (The one filed by the
present applicant as Japanese Patent Application No. 62-114716, etc.) Polysiloxane-based
polymer having a repeating unit consisting of the following general formula and copolymer R
thereof. → 0-3i ← (CHd-rO-R +, wherein R 6 is a lower alkyl group, k is an integer of 3 to 3 °,
and R + has the same meaning as described above.
(IV) Polyester-Based Polymer Liquid Crystal (The one filed by the present applicant as Japanese
Patent Application No. 61-206851) Polyester-based polymer having a repeating unit consisting
of the following general formula and R1 in the copolymer formula thereof is H, CH3 or CtHsl is
an integer of 1 to 20, and k, R, have the same meanings as described above. (V) A polymer liquid
crystal in which the side chain is fixed to the main chain by hydrogen bonding (this can be
inferred from the application of the present applicant as Japanese Patent Application No. 61169288). One or more types of side chains may be used. The average molecular weight of the
polymer liquid crystal used in the present invention as described in (1) to (V) above is 1.000 to 1.
ooo, ooo is preferably 1.000 to 400.000. If it is less than 1 ° 000, the formability of the polymer
liquid crystal as a film or a coating may be impaired, while if it exceeds 400.000, undesirable
results such as slow response speed may appear. is there. The particularly preferable range of
the number average molecular weight depends on the kind of the substituent and the like and
can not be generally defined, but it is usually 1,000 to 200,000. These high molecular weight
liquid crystals may be used in combination as appropriate, as long as the object of the present
invention is not impaired. The polymer liquid crystal according to the present invention may be
any other liquid crystal polymer, olefin resin, acrylic resin, methacrylic resin, polystyrene resin,
polyester resin, polycarbonate resin, as long as the object of the present invention is not
impaired. It is also possible to form a polymer liquid crystal film by mixing it with a usual resin
such as styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer and the like.
However, since the liquid crystallinity is lowered when a large amount of these resins is added,
the weight ratio to the polymer liquid crystal is preferably 2 or less. On the other hand, in order
to improve responsiveness, a ferroelectric low molecular weight liquid crystal, for example, a
liquid crystal compound having a chiral smectic C phase such as p-decyloxybenzylidene-p'amino-2-methylbutylcinnamate (DOBAMQC) is mixed. Can also be used. The mixing ratio is
preferably 5 or less by weight. There is no restriction | limiting in particular as a compounding
method of said each component, It can carry out by blending by a normal method. The
ferroelectric polymer liquid crystal used in the present invention is not limited to the one having
1 or 2 asymmetric carbons at the terminal part of the side chain in the polymer, and the
asymmetric carbon at the terminal part of the side chain The thing containing three or more can
also be used.
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Here, a specific experimental example of a liquid crystal acoustic device using a ferroelectric
polymer liquid crystal as described above will be described. In the first experimental example, as
a ferroelectric polymer liquid crystal, polyacrylate polymer liquid crystal of molecule -5300 is ←
C3lC) I ← C = 00 CL phase transition behavior 10 ° c 61 ° C. 110 ° CCrys →→ s , C "→ → S,
A ← → 11a 9 ° C 60 ° C 96" C, a liquid crystal layer with a film thickness of 5 μm is formed
by a coating method on a glass substrate having an electrode consisting of an ITO film on the
surface A liquid crystal acoustic element was formed by laminating an electrode-attached PET
film of ITO film from the above. When such a liquid crystal acoustic element is maintained at 20
° ((s, c ′ ′ phase) and an IKI (z 20 V sine wave) is applied as an audio signal voltage,
generation of a plane wave is confirmed from the surface and its sound pressure level Was about
60 dB at 1 m. In addition, although the S and A phases are at 70 ° C., since each liquid crystal
molecule has a dipole, sound generation is also possible, and a relatively large sound output of
about 55 dB is obtained by applying the same <1 KH 220 V sine wave. It was done. Next, when
the frequency of the audio signal voltage was changed from direct current to 1 MHz, an & f flat
characteristic was obtained from about 30 Hz to 45 KHz, and an output variation width over the
entire region of ± 10 dB1000 was obtained. In addition, it was also confirmed that the image
display operation is simultaneously possible according to the procedure of the embodiment in
the state where the temperature is maintained at 20 ° C. (s, c ′ ′ phase). In the second
experimental example, 強 0 CI (ICH → 1, as a ferroelectric polymer liquid crystal). Using the
phase transition behavior, a liquid crystal phase oriented by the coating method is formed in the
same manner as in the first experimental example, and the liquid crystal phase can be held
between two ITO films with an electrode attached film and a whole film can be bent. Liquid
crystal acoustic element. Here, the alignment of the liquid crystal phase in the present
experimental example is such that good contrast of 50 or more can be obtained at a display
signal voltage of ± IOV at 25 ° C. (S, C ′ ′ phase), and the first embodiment Sound can be
generated simultaneously with image display by applying a similar audio signal voltage. For
example, under an audio signal voltage of display signal voltage ± IOV, amplitude 20 V and
frequency 4 KHz, a sound pressure level of 68 dB is obtained along with image display. It was
done. In addition, even if the liquid crystal acoustic device of this experimental example was bent
to a curvature radius of 501 m, both image display and sound generation could be used without
any problem. As a comparative example, a similar element was fabricated using DOBAMBC which
is a low molecular ferroelectric liquid crystal.
In addition, since low molecular ferroelectric liquid crystals such as DOBAMBC are difficult to
align by the coating method, they are coated with polyimide. ■ TO II! Alignment treatment was
performed by rubbing using an electrode-attached electrode substrate. Here, when the cell
thickness is about 2 μm using a 5iO 8 spacer, the contrast when applying the display signal
voltage of ± IOV is 12 even at about 70 ° C., which is the same as the first experimental
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example A sound pressure level of 53 dB L was not obtained when applying an audio signal
voltage of 1 KHz and 20 V. Therefore, when a ferroelectric polymer liquid crystal is used for the
liquid crystal acoustic element, compared with the case where a low molecular weight
ferroelectric liquid crystal is used, easiness of manufacture, flexibility, obtained sound pressure
level, contrast when displaying an image, etc. The superiority of each is evident. [Effects of the
Invention] As described above, according to the liquid crystal acoustic device of the present
invention, by using the ferroelectric polymer liquid crystal for the liquid crystal layer, it is
possible to generate sound with high efficiency and to align the liquid crystal. The image display
function can be obtained simultaneously and easily. In addition, since it is a polymer, it is
possible to have a film forming property, to easily increase the area, and to have flexibility, and
since the transparent electrode may be printed on a transparent substrate such as a film, the
manufacture is easy. The productivity is high, and can be provided inexpensively.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a partially cutaway perspective view showing a schematic configuration of an
embodiment of the liquid crystal acoustic device according to the present invention, FIG. 2 is a
sectional view of FIG. 1, and FIG. 3 shows applied voltages in the embodiment. It is a graph.
10: liquid crystal acoustic element, 11.15: transparent substrate, 12.14: transparent electrode,
13: liquid crystal layer using ferroelectric polymer liquid crystal, 16.17: polarizing plate .
Application 5 people Idemitsu Kosan Co., Ltd.
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