Reflecting cholesteric LCD having viewer side layer which either scatters or transmits light depending on angle

A reflecting liquid crystal display unit that reflects light entering from an observer side to display an image. The reflecting liquid crystal display has a composite layer of cholesteric liquid crystal material and polymer resin, and an an isotropic scattering layer. The an isotoropic scattering layer scatters light entering this layer at a relative large incident angle passes light entering this layer at a relative small incident angle. The an isotoropic scattering layer is provided on an observer side of the composite layer.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a reflecting liquid crystal display unit
 that performs display via reflection using liquid crystal.
 2. Description of the Related Art
 Various types of liquid crystal display units have conventionally been
 proposed. For example, a TFT liquid crystal device in which each pixel has
 a thin film transistor has been put into practical use. While a TFT liquid
 crystal device is capable of high precision display, it requires a precise
 and complex manufacturing process. Moreover, the manufacturing yield for
 such devices is poor, leading to an increase in costs.
 With this as a backdrop, a polymer-based dispersed liquid crystal device,
 which is relatively easy to manufacture, has been drawing attention. This
 liquid crystal device uses a layer containing a composite of liquid
 crystal and polymer, which is created by dispersing a liquid crystal in a
 polymer material. For example, U.S. Pat. No. 5,437,811 discloses a liquid
 crystal display unit that performs color display by means of the selective
 reflection characteristic of a liquid crystal that exhibits a cholesteric
 characteristic. This liquid crystal device performs display via reflection
 using the focal conic state (a colored transparent state) and the planar
 state (a scattering state) of a chiral nematic liquid crystal. The focal
 conic state is a state in which the helical axes of liquid crystal
 molecules are aligned in a random fashion, whereas the planar state is a
 state in which the helical axes of liquid crystal molecules are aligned
 parallel to one another. This liquid crystal element scatters incident
 light in the focal conic state and selectively reflects light of a certain
 wavelength in the planar state. The liquid crystal device changes from the
 planar state to the focal conic state with the application of low voltage
 pulses, while it changes from the focal conic state to the planar state
 with the application of high voltage pulses.
 Generally, the two states of said liquid crystal that exhibits a
 cholesteric characteristic have a stable memory capability. That is, even
 after the cease of voltage pulses, these states are maintained. Therefore,
 high precision display becomes possible using merely a simple matrix drive
 without the need for a complex circuit using active elements as in the
 case of TFT liquid crystal.
 In the planar state, liquid crystal selectively reflects the light
 component having a specific wavelength among the rays of the incident
 light which enters the liquid crystal in parallel to the helical axes of
 the liquid crystal. The specific wavelength .lambda. corresponds to
 helical pitch p and average refractive index n of the liquid crystal, that
 is, .lambda.=n.times.p. The light that enters the liquid crystal parallel
 to the helical axes when the liquid crystal is in the planar state is
 divided into two types of circular polarization, i.e., right rotary
 polarization and left rotary polarization. The light component for one
 rotary direction passes through the liquid crystal while the light
 component for the other rotary direction is reflected completely by the
 liquid crystal. This property is called circular polarization dichroism.
 Because of this property, the reflection rate of the display unit in the
 planar state, i.e., the selective reflection state, is 50% at the maximum,
 and therefore where the planar state is used as a bistable display state,
 the luminance of the display is limited.
 In order to resolve this problem, U.S. Pat. No. 5,408,344, for example,
 proposes a technology in which the luminance is improved by inserting a
 reflecting layer, located between the liquid crystal layer and the light
 absorbing layer (namely, opposite the observer side of the liquid crystal
 layer), having a scattering characteristic that varies depending on the
 angle of the incident light.
 However, display units that use conventionally proposed liquid
 crystal-polymer composite layers have a problem that, where the
 illuminating light is fixed, the peak wavelength of the reflected light
 fluctuates greatly depending on the viewing angle, and the color of the
 display changes accordingly when observed. For example, if a reflecting
 liquid crystal display unit is placed on an indoor wall, e.g., a wall of a
 meeting room, light enters the liquid crystal display device at an angle
 from the illuminating source located on the ceiling. In such an
 environment, the display color changes depending on where the observer is
 situated.
 SUMMARY OF THE INVENTION
 The present invention was made in consideration of these problems. The main
 object of the present invention is to provide an improved reflecting
 liquid crystal display unit.
 Another object of the present invention is to provide a reflecting liquid
 crystal display unit that has a sufficiently high luminance.
 The third object of the present invention is to provide a reflecting liquid
 crystal display unit in which the reflected light's peak wavelength is
 less dependent on the viewing angle.
 The fourth object of the present invention is to provide a reflecting
 liquid crystal display unit that has a sufficiently high luminance and in
 which the reflected light's peak wavelength is less dependent on the
 viewing angle.
 In order to attain at least one of the objects described above, the
 reflecting liquid crystal display unit of the present invention has an
 anisotropic light scattering layer on the observer side of the liquid
 crystal layer. It is preferred that the liquid crystal layer include a
 cholesteric liquid crystal. For cholesteric liquid crystal, a chiral
 nematic liquid crystal in which a chiral ingredient is added to a nematic
 liquid crystal may be used. The liquid crystal layer may also be a layer
 comprising a liquid crystal-polymer resin composite, for example. The
 composite layer may be prepared, for example, by mixing a photopolymer
 resin and a liquid crystal and then photopolymerizing the mixture. The
 anisotropic light scattering layer is a layer which selectively scatters
 the incident light depending on the incident angle at which the light
 enters it. The anisotropic light scattering layer preferably scatters the
 light that enters it at a relatively sharper angle and lets pass the light
 that enters it at angles closer to a right angle. The anisotropic light
 scattering layer may be placed on the outermost surface of the liquid
 crystal display unit facing the observer, but it may be located elsewhere
 as well.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The embodiments of the present invention are explained below with reference
 to the drawings.
 1. FIRST EMBODIMENT
 As shown in FIG. 1, liquid crystal display unit 100 comprises transparent
 base 55, transparent electrodes 14, liquid crystal-polymer composite layer
 (simply referred to as `composite layer` below) 10 to perform display of a
 specific color, transparent electrodes 13, transparent base 50 and
 anisotropic light scattering layer 70, said members being placed one on
 top of the other in said sequence. Transparent electrodes 13 and 14, e.g.,
 ITO electrodes, are connected to power supply 80 such that voltage may be
 applied to composite layer 10.
 In this embodiment, the upper side of liquid crystal display unit 100 in
 FIG. 1 is the observer side. If light is projected onto liquid crystal
 display unit 100 from the upper side when the liquid crystal of composite
 layer 10 (liquid crystal that exhibits a cholesteric characteristic,
 hereinafter simply referred to as `cholesteric liquid crystal`) is in the
 planar state, composite layer 10 reflects light of a specific wavelength
 from among the rays of incident light. Where this specific wavelength is
 set within the visible light range, liquid crystal display unit 100
 performs display of a color of said specific wavelength. On the other
 hand, where the specific wavelength is set outside the visible light
 range, i.e., in the infrared light range, for example, composite layer 10
 reflects infrared light and lets pass visible light, and consequently
 liquid crystal display unit 100 appears transparent to the observer. Where
 light absorbing member 60 (a black plate or black film, for example) is
 placed behind liquid crystal display unit 100 (opposite from the observer
 side), as shown in FIG. 1, liquid crystal display unit 100 appears black
 to the observer because the visible light that passed through composite
 layer 10 is absorbed by light absorbing member 60. Light absorbing member
 60 may be substituted for by the application of a black paint, such as a
 black ink, onto the surface farthest from the observer, for example.
 If light is projected onto liquid crystal display unit 100 from the upper
 side when the cholesteric liquid crystal of composite layer 10 is in the
 focal conic state, composite layer 10 scatters or lets pass the incident
 light depending on the characteristics of the liquid crystal that is used.
 Where birefringence .DELTA.n is small, as a characteristic of the liquid
 crystal, or where the domain of the liquid crystal is small, composite
 layer 10 lets pass the visible light component of the incident light when
 it is in the focal conic state. Therefore, liquid crystal display unit 100
 appears transparent to the observer in this case (black if light-absorbing
 member 60 is used). On the other hand, where birefringence .DELTA.n is
 large, as a characteristic of the liquid crystal, or where the domain of
 the liquid crystal is large, composite layer 10 scatters the visible light
 component of the incident light when it is in the focal conic state.
 Therefore, liquid crystal display unit 100 appears white to the observer
 in this case. Here, birefringence .DELTA.n mentioned above may be obtained
 from the equation .DELTA.n=n.sub.1 -n.sub.2, where n.sub.1 is the
 refractive index of the liquid crystal molecule along its length and
 n.sub.2 is the refractive index of the liquid crystal molecule along the
 direction perpendicular to its length.
 The liquid crystal of composite layer 10 switches from the focal conic
 state to the planar state, or vice versa, in response to the two types of
 voltage that are applied, i.e., high and low voltage. Specifically, when
 low voltage signal is applied to composite layer 10, the liquid crystal
 exhibits the focal conic state following the application of the voltage.
 When high voltage signals are applied to composite layer 10, the liquid
 crystal exhibits the planar state following the application of the
 voltage. It is preferable that a pulse voltage be used, as mentioned
 above, for the voltage that is applied between the transparent electrodes
 in order to switch the state of composite layer 10.
 Anisotropic light scattering layer 70 allows light that enters the observed
 surface from an angle within a prescribed range relative to the normal
 line of said surface to advance straight ahead (i.e., pass through) and
 scatters light that enters said surface from an angle outside said
 prescribed range. For anisotropic light scattering layer 70, Sumitomo
 Chemical Co., Ltd.'s field of view regulating film "Lumisty" series, for
 example, is available. By placing said anisotropic light scattering layer
 70 on the observer side of composite layer 10, light that enters at an
 angle may be scattered on the surface of the anisotropic light scattering
 layer 70. By the scattering, incident angle of some component of the light
 is changed to relatively small. Moreover, by the scattering, the light
 which would be reflected by the surface of the liquid crystal display unit
 can enter to the composite layer. Consequently, the amount of light
 entering composite layer 10 increases and the luminance of the display
 increases accordingly. Moreover, the selective reflection wavelength of
 cholesteric liquid crystal generally becomes shorter as the incident angle
 or reflection angle increases. Therefore, the larger the viewing angle,
 the greater the color discrepancy. However, as described above, the
 illuminating light that enters liquid crystal display unit 100 at an angle
 enters composite film 10 as scattered light because of the existence of
 anisotropic light scattering layer 70, and consequently, the incident
 angle of the incident light with regard to the composite layer decreases
 overall and the occurrence of color discrepancy may be reduced.
 Paired transparent electrodes 13 and 14 each comprise a plurality of strip
 electrodes that are aligned parallel to one another with small spaces in
 between. Transparent electrodes 13 and 14 face each other such that the
 direction of alignment of the strip electrodes of electrodes 13 is
 perpendicular to that of the alignment of the strip electrodes of
 electrodes 14. Display is performed when electricity is sequentially
 provided to these strip electrodes 13 and 14, the former being above the
 latter, and voltage is sequentially applied in a matrix fashion to
 composite layer 10. Liquid crystal display unit 100 can perform image
 display based on said matrix drive.
 For composite layer 10, a composite layer that may be obtained by
 projecting light, such as ultraviolet light, onto a mixture of a liquid
 crystal and a photo-cured resin material such that the resin is hardened
 and the liquid crystal and resin are separated is applicable. The
 construction of this composite layer may be such that the resin has a
 three-dimensional mesh construction and the liquid crystal fills the gaps
 in the resin, or such that multiple liquid crystal droplets are surrounded
 by the resin. The construction may also be one in which the resin forms
 multiple pillars formed between the upper and lower bases and the spaces
 formed among these pillars are filled by the liquid crystal. These
 composite layer constructions may be controlled by means of the ratio
 between the photopolymer resin material and the liquid crystal, the speed
 of photopolymerization, etc. The composite layer may also be made by
 forming a resin construction as described above and then pouring a liquid
 crystal into the gaps in said resin construction.
 For the liquid crystal used in the composite layer 10, for example,
 cholesteric liquid crystal may be used as described above. Cholesteric
 liquid crystal, as a whole, has a multi-layer construction. In each layer,
 the lengthwise axes of the liquid crystal molecules are aligned parallel
 to one another. The lengthwise axes of the molecules of these liquid
 crystal layers are angled slightly relative to the neighboring layers such
 that the molecules show a spiral construction as a whole.
 For the cholesteric liquid crystal, a liquid crystal that exhibits a
 cholesteric characteristic at room temperature is particularly preferred.
 In case of a display unit that is used in an environment where the
 temperature is relatively high, a cholesteric liquid crystal that exhibits
 a cholesteric characteristic in that environment is preferred. For the
 cholesteric liquid crystal, a chiral nematic liquid crystal, which is
 obtained by adding a chiral ingredient to a nematic liquid crystal, may be
 used. In a nematic liquid crystal, sticklike liquid crystal molecules are
 aligned parallel to one another but no layer construction is present. A
 chiral ingredient is an additive that twists the nematic liquid crystal
 molecules when added to a nematic liquid crystal. By adding a chiral
 ingredient to a nematic liquid crystal, a spiral construction with a
 prescribed pitch is formed with regard to the liquid crystal molecules,
 and this generates a cholesteric characteristic.
 By changing the amount of chiral ingredient added to nematic liquid
 crystal, the pitch of the spiral construction of the chiral nematic liquid
 crystal can be changed, through which the selective reflection wavelength
 of the liquid crystal may be controlled. Generally, the helical pitch that
 is defined as the distance between molecules when liquid crystal molecules
 rotate 360 degrees along the spiral construction (i.e., the distance
 between layers) is used as a term that expresses the pitch of the spiral
 construction of liquid crystal molecules.
 For a chiral ingredient, cholesteric liquid crystal having a cholesteric
 ring, chiral nematic liquid crystal and organic compounds that act to
 twist the molecules of nematic liquid crystal but do not show liquid
 crystal characteristics themselves may be used. For such organic
 compounds, a commonly marketed chiral doping agent--representative
 examples include Merck's organic compounds S811, S1011, etc.,--may be
 used.
 More than one chiral ingredient may be mixed and used. The use of more than
 one chiral doping agent is effective in increasing the phase change
 temperature (the NI point) of the liquid crystal, reducing the change in
 the selective reflection wavelength that occurs as temperature changes,
 improving the transparency of the composite layer in the transparent
 state, and speeding up the switching between the transparent state and the
 selective reflection state of the liquid crystal display
 unit--particularly color liquid crystal display units, etc.
 Composite layer 10 may be switched between a light pass-through state in
 which visible light is allowed to pass through and a selective reflection
 sate in which visible light of a specific wavelength is selectively
 reflected, or between a light scattering state in which visible light is
 scattered and a light pass-through state in which visible light is allowed
 to pass through, in response to the application of a specific voltage.
 Each state may be maintained even after the cease of voltage application.
 In the case of composite layer 10 in which a chiral nematic liquid crystal
 is used, in particular, the state of alignment of the liquid crystal
 molecules may be switched between the planar state and the focal conic
 state by applying two types of pulse voltage, e.g., high and low pulse
 voltage.
 Three layers may be formed as composite layer 10 in which a chiral nematic
 liquid crystal is used. In this case, the helical pitch may be adjusted by
 adjusting the amount of chiral ingredient added to the nematic liquid
 crystal of each layer, and the selective reflection wavelength in each
 layer may be set to red light, green light and blue light. By setting each
 layer in this way, each layer may have a selective reflection state
 colored red, green or blue when the liquid crystal molecules are in a
 planar alignment and a transparent light pass-through state when they are
 in a focal conic alignment. A liquid crystal display unit capable of color
 display may thus be provided.
 In addition, if the amount of the chiral ingredient added is adjusted so as
 to adjust the helical pitch of the chiral nematic liquid crystal such that
 the selective reflection wavelength is set to infrared light, composite
 layer 10 is obtained that exhibits a transparent light pass-through state
 when the liquid crystal molecules are in a planar alignment and a light
 scattering state in which it appears white due to isotropic scattering
 when the liquid crystal molecules are in a focal conic alignment. By
 sandwiching composite layer 10 thus obtained between transparent
 electrodes, a white display unit may be obtained.
 The relationship between helical pitch p (nm) and selective reflection
 wavelength .lambda. (nm) is expressed by the following equation [I].
EQU .lambda.=n.times.p [I]
 where, n represents the average refractive index and n.sup.2
 =(n.sub.1.sup.2 +n.sub.2.sup.2)/2.
 In order to make a color liquid crystal display unit that performs color
 display of various colors or a white liquid crystal display unit that
 performs white display, a method in which a mixture of liquid crystal and
 photo-cured resin material is sandwiched between a pair of transparent
 electrodes and the photo-cured resin material of the mixture is hardened
 by projecting light such as ultraviolet light onto the mixture such that
 the liquid crystal and the resin are separated. When this is done, if
 spacers are placed or dispersed between the electrodes together with the
 mixture, the thickness of composite layer 10 may be more easily
 controlled.
 For the photo-cured resin material, a mixed solution of either a
 photo-cured monomer or an oligomer and a photopolymerization starting
 agent may be used. In this case, the photopolymerization separating method
 may be used in which the mixture solution and a liquid crystal are mixed
 and the resin material is then photo-cured by projecting ultraviolet light
 onto it, such that the liquid crystal and the resin are separated.
 2. SECOND EMBODIMENT
 An example in which the liquid crystal display unit itself has electrodes
 was described in the first embodiment, but so long as an electric field is
 made to work so that the liquid crystal switches between a transparent
 state and a selective reflection state, the liquid crystal display unit
 itself need not necessarily have electrodes. Therefore, in this
 embodiment, an example in which electrodes to apply voltage to the
 composite layer are located outside the liquid crystal display unit will
 be explained.
 FIG. 2 shows a cross-sectional view of liquid crystal display sheet 200,
 one form of the second embodiment. As shown in FIG. 2, liquid crystal
 display sheet 200 comprises transparent base 55, composite layer 10 to
 perform display of a specific color, and transparent base 50, said members
 being placed one on top of the other in said sequence. Anisotropic light
 scattering layer 70 is formed on the outermost surface closest to the
 observer in the same manner as in the first embodiment. As shown in FIG.
 2, a pair of electrodes 81 and 82 that are connected to power supply 80
 are placed on the top and bottom surfaces of liquid crystal display sheet
 200, and the alignment of the liquid crystal molecules may be changed and
 display performed by applying voltage to liquid crystal display sheet 200.
 FIG. 3 shows one specific construction of the second embodiment that allows
 liquid crystal display sheet 200 to perform display. As shown in FIG. 3,
 this system is equipped with conveyance rollers 90 and 91, electrodes 83
 that are placed along the width of liquid crystal display sheet 200 and
 power supply 80 to which electrodes 83 are connected.
 By individually driving electrodes 83 based on image information while
 feeding the display sheet at a certain speed by means of conveyance
 rollers 90 and 91, an image may be formed on liquid crystal display sheet
 200. By applying a uniform voltage via electrodes 83, the image on the
 sheet may be erased.
 FIG. 4 shows another specific construction of the second embodiment for the
 application of voltage. As shown in FIG. 4, a desired image may be formed
 on liquid crystal display sheet 200 by placing liquid crystal display
 sheet 200 on electrode plate 85 and moving pen-type electrode 84, which is
 connected to power supply 80, on liquid crystal display sheet 200. In this
 construction as well, an anisotropic light scattering layer is placed on
 the surface of liquid crystal display sheet 200 facing the observer.
 The present invention is explained in more detail below with reference to
 specific experimental examples.
 3. EXPERIMENTAL EMBODIMENT 1
 A mixture made by mixing MN1008XX (from Chisso Corp.) and M15 (from Merck)
 at a weight ratio of 85:15 was used for the nematic liquid crystal. Chiral
 ingredient S811 (from Merck) was added to this nematic liquid crystal in
 20 wt % to prepare a chiral nematic liquid crystal having a selective
 reflection wavelength of 1100 nm. Here, MN1008XX is a liquid crystal
 having tolane compound as its main component and having the physical
 properties shown below.
EQU .DELTA.n=0.218 (.lambda.=589 nm, 25.degree. C.)
EQU T.sub.N-1 =73.9.degree. C.
EQU V.sub.90 =2.16V
EQU .eta..sub.20 =31.4 cps
 A photo-cured resin material was then prepared by adding
 photopolymerization starting agent DAROCURE 1173 (from Ciba Geigy) in 3 wt
 % to monofunctional monomer R128H (from Nippon Kayaku).
 The chiral nematic liquid crystal and photo-cured resin material described
 above were mixed together with a weight ratio of 85:15. It was then
 sandwiched between two glass substrates that had transparent conductive
 films on their surfaces, such that the transparent conductive films would
 be inside, together with 10 .mu.m spacers. A 15 mW/cm.sup.2 ultraviolet
 light was then projected onto the mixture for three minutes at room
 temperature so that the resin would harden and the resin and the liquid
 crystal would separate. Further, a field of view regulating film (Lumisty
 Z-3030 from Sumitomo Chemical Co., Ltd.) was placed on the observation
 surface as an anisotropic light scattering layer and a black light
 absorbing member was placed on the back. A liquid crystal display unit
 having the construction shown in FIG. 1 was thus obtained. The anisotropic
 light scattering layer has a characteristic by which it scatters incident
 light that enters it within the range of 30 to 60 degrees relative to its
 normal line (that is, incident angle within 30 to 60 degrees), becoming
 nontransparent, and lets incident light outside said range pass through,
 becoming transparent.
 The selective reflection wavelength of the liquid crystal-polymer composite
 layer was set to be 100 nm. Therefore, the composite layer reflects light
 in the infrared range and becomes transparent when the liquid crystal
 molecules are put in a planar alignment by means of the application of
 high voltage pulses, while the level of scattering increases and the
 composite layer becomes white when the liquid crystal molecules are put
 into a focal conic alignment by means of the application of low voltage
 pulses. In other words, the liquid crystal display unit becomes a black
 and white display unit.
 The luminance of the liquid crystal display unit thus prepared, relative to
 the viewing angle, was then investigated. FIG. 5 shows the principle of
 the measurement method regarding the luminance. As shown in FIG. 5, the
 luminance of the liquid crystal display unit relative to the viewing angle
 (.beta. in FIG. 5) was measured by placing light source 500 at a 45 degree
 angle (.alpha. in FIG. 5) relative to normal line P of the liquid crystal
 display unit to project light and measuring the luminance while changing
 the position of luminance meter 510 as if drawing an arc in a plane
 perpendicular to the plane including normal line P and the direction of
 projection of light source 500, with the point at which the light enters
 the display unit as the center of said arc. A fluorescent light was used
 for the light source and an LS100 (from Minolta) was used for the
 luminance meter. In addition, the spectral reflectance of each display
 unit explained below was also measured in the same manner.
 FIG. 6 shows the results of the measurement. The upper solid line in FIG. 6
 indicates the luminance when the liquid crystal was in the scattering
 state, that is, the focal conic state. The lower solid line in FIG. 6
 indicates the luminance when the liquid crystal was in the transparent
 state, that is, the planar state. For comparison purposes, FIG. 6 also
 shows, using dotted lines, the results for the liquid crystal display unit
 of comparison example 1, which was the display unit of experimental
 example 1 from which the anisotropic light scattering layer was omitted.
 As shown in FIG. 6, while the luminance of the liquid crystal display unit
 was essentially the same as that of comparison example 1 when in the
 transparent state, the luminance increased by around 20% relative to
 comparison example 1 in which the liquid crystal display unit was in the
 scattering state.
 4. EXPERIMENTAL EXAMPLE 2
 Chiral ingredients S811 (from Merck) and CN (from Merck) were added in 9 wt
 % and 18 wt %, respectively, to nematic liquid crystal MN 1000XX (from
 Chisso Corp.) to prepare a chiral nematic liquid crystal having a
 selective reflection wavelength of 630 nm. Here, MN1000XX is a liquid
 crystal having a tolane compound as its main component and having the
 physical properties shown below.
EQU .DELTA.n=0.219 (.lambda.=589 nm, 25.degree. C.)
EQU T.sub.N-1 =69.9.degree. C.
EQU V.sub.90 =2.29V,
EQU .eta..sub.20 =30.6 cps
 A photo-cured resin material was then prepared by adding
 photopolymerization starting agent DAROCURE 1173 (Ciba Geigy) in 3 wt % to
 monofunctional monomer MPL-212 (from Nippon Kayaku) to which bifunctional
 monomer BF530 was added in 20 wt %.
 The chiral nematic liquid crystal and the photo-cured resin material
 described above were mixed in a weight ratio of 85:15. Said mixture was
 then sandwiched between two glass substrates having transparent conductive
 films on the surfaces such that the transparent conductive films would be
 inside, together with 10 .mu.m spacers. A 15 mW/cm.sup.2 ultraviolet light
 was then projected onto the mixture for three minutes at room temperature
 so that the resin would harden and the liquid crystal and the resin
 material would separate. Further, a field of view regulating film (Lumisty
 Z-3030 from Sumitomo Chemical Co., Ltd.) was placed on the observation
 surface as an anisotropic light scattering layer, while a black
 light-absorbing member was placed on the back, and a liquid crystal
 display unit was thus obtained.
 The composite layer of the liquid crystal display unit prepared in this way
 reflects red light and appears red when the liquid crystal molecules are
 put in a planar alignment by means of the application of high voltage
 pulses, and when the molecules are put into the focal conic alignment by
 means of the application of low voltage pulses, the composite layer
 becomes transparent. In other words, the liquid crystal display unit
 becomes a red and black display unit.
 The luminance of the liquid crystal display unit prepared in this way with
 reference to the viewing angle was investigated using the same method that
 was used for experimental example 1. FIG. 7 shows the results of the
 measurement. The upper solid line in FIG. 7 shows the luminance when the
 liquid crystal was in the selective reflection state, that is, the planar
 state. The lower solid line in FIG. 7 shows the luminance when the liquid
 crystal was in the transparent state, that is, the focal conic state. FIG.
 7 also shows, using dotted lines, the results for the liquid crystal
 display unit of comparison example 2, which was the display unit of
 experimental example 2 from which the anisotropic light scattering layer
 was omitted. As shown in FIG. 7, while the luminance of the liquid crystal
 display unit was essentially the same as that of comparison example 2 when
 in the transparent state, it increased by approximately 20% relative to
 comparison example 2 when in the selective reflection state.
 In the case of this example, because the selective reflection wavelength is
 set to the visible light range, it is not preferred in practical use if
 the selective reflection wavelength varies depending on the viewing angle.
 Therefore, in this experimental example, the dependence of the selective
 reflection wavelength (light dispersion spectrum peak wavelength) on the
 viewing angle was measured.
 For the measurement, a tungsten lamp was used for the light source. The
 measurement was performed in the same manner as the measurement of
 luminance using a spectro multi channel photo detector (MCPD-2000 from
 Otsuka Electronics).
 The results are shown in FIG. 8 using a solid line. FIG. 8 also shows for
 comparison purposes, using a dotted line, the results for the display unit
 of comparison example 2. As is clear from FIG. 8, the differences between
 viewing angles in terms of the peak selective reflection wavelength are
 smaller than for the display unit of comparison example 2.
 5. EXPERIMENTAL EXAMPLE 3
 A liquid crystal display unit was prepared using the same procedure used
 for experimental example 2 except that the amounts of chiral doping agents
 S811 (from Merck) and CN (from Merck) added to the nematic liquid crystal
 were 10 wt % and 20 wt %, respectively, so that a chiral nematic liquid
 crystal having a selective reflection wavelength of 550 nm would be
 obtained.
 The composite layer of the liquid crystal display unit prepared in this way
 reflects green light and appears green when the liquid crystal molecules
 are put into a planar alignment by means of the application of high
 voltage pulses, while the composite layer becomes transparent when the
 liquid crystal molecules are put into a focal conic alignment by means of
 the application of low voltage pulses. In other words, the liquid crystal
 display unit becomes a green and black display unit.
 The luminance of the liquid crystal display unit prepared in this way with
 reference to the viewing angle was investigated using the same method that
 was used for experimental example 1. FIG. 9 shows the results of the
 measurement. The upper solid line in FIG. 9 indicates the luminance when
 the liquid crystal was in the selective reflection state, that is, the
 planar state. The lower solid line in FIG. 9 indicates the luminance when
 the liquid crystal was in the transparent state, that is, the focal conic
 state. FIG. 9 also shows for comparison purposes, the results for the
 liquid crystal display unit of comparison example 3, which was the display
 unit of experimental example 3 from which the anisotropic light scattering
 layer was omitted. As shown in FIG. 9, the luminance of the liquid crystal
 display unit of experimental example 3 was essentially the same as that of
 comparison example 3 when in the transparent state, while it increased by
 about 20% relative to comparison example 3 when in the selective
 reflection state.
 The dependence of the reflection wavelength spectrum of this liquid crystal
 display unit on the viewing angle was measured using the same procedure
 that was used for experimental example 2. FIG. 10 shows the results using
 a solid line. FIG. 10 also shows for comparison purposes, using a dotted
 line, the results for the display unit of comparison example 3. As is
 clear from FIG. 10, the differences between viewing angles in terms of the
 peak selective reflection wavelength are smaller in comparison with the
 construction of comparison example 3.
 In the embodiments explained above, a construction in which the anisotropic
 light scattering layer is placed on the outermost surface that faces the
 observer was explained, but the present invention is not limited to this.
 It is acceptable as long as the anisotropic light scattering layer is
 located closer to the observer than the liquid crystal layer.
 Although the present invention has been fully described by way of examples
 with reference to the accompanying drawings, it is to be noted that
 various changes and modifications will be apparent to those skilled in the
 art. Therefore, unless otherwise such changes and modifications depart
 from the scope of the present invention, they should be construed as being
 included therein.