JP2009294320A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which the pretilt azimuth of a liquid crystal molecule on a reflective electrode is stably defined by using a PSA technology. <P>SOLUTION: A pixel includes: a liquid crystal layer 42 including nematic liquid crystal material of negative dielectric anisotropy; a pixel electrode 14 and a counter electrode 24 facing each other via the liquid crystal layer; vertically aligned films 32a, 32b; and a pair of alignment sustained layers 34a, 34b constituted with a UV polymer formed on respective surfaces of the liquid crystal layer sides of the vertically aligned films. The pixel electrode has a reflective electrode 14R that reflects visible light, the reflective electrode transmits UV ray and the alignment sustained layer is formed on the liquid crystal layer side of the reflective electrode, too. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device capable of displaying in a reflection mode.

  Currently, as a liquid crystal display device having a wide viewing angle characteristic, a horizontal electric field mode (including an IPS mode and an FFS mode) and a vertical alignment (VA) mode are used. Since the VA mode is more mass-productive than the horizontal electric field mode, it is widely used for TV applications and mobile applications. In addition, a VA mode liquid crystal display device performs display in normally black using a vertical alignment type liquid crystal layer including a nematic liquid crystal material having negative dielectric anisotropy and a pair of polarizing plates arranged in crossed Nicols. Therefore, it has the feature that the quality of black display is high.

  As a VA mode liquid crystal display device, an MVA mode (see Patent Document 1) and a CPA mode (see Patent Document 2) are known. Patent Document 3 discloses a liquid crystal display device having four domains formed by providing a cross-shaped slit in a counter electrode.

  The above MVA mode is used to obtain a sufficient alignment regulating force when a slit formed in an electrode is used as an alignment regulating means (or domain regulating means) for regulating the direction in which liquid crystal molecules are tilted when a voltage is applied. The width of the slit needs to be about 10 μm or more, and is not suitable for small pixels (for example, short sides of less than 100 μm, particularly less than 60 μm). In addition, although the CPA mode can obtain a high transmittance by arranging a quarter-wave plate between the liquid crystal layer and the polarizing plate, it has a low contrast ratio and a narrow viewing angle compared to the MVA mode. There is.

  On the other hand, when four domains are formed using the cross slits described in Patent Document 3, when a sufficiently high voltage is applied to the liquid crystal layer, an oblique electric field generated at the edge portion of the pixel electrode is opposed to Due to the oblique electric field generated in the vicinity of the cross slit of the electrode, four domains in which the orientation directions (domain directors) of the liquid crystal molecules differ from each other by approximately 90 ° can be formed. This alignment division structure is sometimes referred to as a 4D structure. When the horizontal slit of the cross slit is the X axis and the vertical slit is the Y axis, the azimuth angle of the director of each domain formed in the first, second, third and fourth quadrants of the pixel is 45 °. , 135 °, 225 ° and 315 °. When the polarization axes of the pair of polarizing plates are arranged parallel to the X-axis and the Y-axis, the region corresponding to the cross slit is dark and the other regions exhibit a uniform high transmittance.

  However, in this configuration, as a matter of course, since the alignment regulating force is expressed only when a voltage is applied, a sufficient alignment regulating force cannot be obtained when the applied voltage is low. Accordingly, there is a problem that the orientation of liquid crystal molecules is not stabilized particularly at a gradation lower than the intermediate gradation, and thus it has not been put into practical use.

On the other hand, in recent years, Polymer Sustained Alignment Technology (hereinafter referred to as “PSA technique”) has been developed as a technique for controlling the pretilt direction of liquid crystal molecules (see Patent Documents 4 and 5 and Non-Patent Document 1). In the PSA technology, a small amount of a polymerizable material (for example, a photopolymerizable monomer) is mixed in a liquid crystal material, and after assembling a liquid crystal cell, a predetermined voltage is applied to the liquid crystal layer and the active energy is applied to the polymerizable material. This is a technique in which the pretilt direction of liquid crystal molecules is controlled by a polymer produced by irradiating a line (for example, ultraviolet rays). The alignment state of the liquid crystal molecules when the polymer is generated is maintained (stored) even after the voltage is removed (a state where no voltage is applied). Therefore, the PSA technique has an advantage that the pretilt azimuth and pretilt angle of the liquid crystal molecules can be adjusted by controlling the electric field formed in the liquid crystal layer. Further, since the PSA technique does not require a rubbing process, it is particularly suitable for forming a vertical alignment type liquid crystal layer in which it is difficult to control the pretilt direction by the rubbing process. The entire disclosures of Patent Documents 4 and 5 and Non-Patent Document 1 are incorporated herein by reference.
Japanese Patent Laid-Open No. 11-242225 JP 2002-202511 A Japanese Patent Application Laid-Open No. 06-43461 JP 2002-357830 A JP 2006-78968 A K. Hanaoka et al. "A New MVA-LCD by Polymer Sustained Alignment Technology", SID 04 DIGEST, pp.1200-1203 (2004)

  However, when the PSA technology using a photopolymerizable monomer is applied to a liquid crystal display device having a reflective electrode, a photopolymer cannot be sufficiently formed on the reflective electrode, and as a result, liquid crystal molecules on the reflective electrode are not formed. There was a problem that the pretilt direction of the lens could not be regulated stably.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a liquid crystal display device in which the pretilt azimuth of liquid crystal molecules on a reflective electrode is stably defined using the PSA technique.

  The liquid crystal display device of the present invention is a liquid crystal display device having a plurality of pixels, and each of the plurality of pixels includes a liquid crystal layer including a nematic liquid crystal material having negative dielectric anisotropy and the liquid crystal layer interposed therebetween. The pixel electrode and the counter electrode facing each other, a pair of vertical alignment films provided between the pixel electrode and the liquid crystal layer and between the counter electrode and the liquid crystal layer, and the pair of vertical alignment films A pair of alignment sustaining layers composed of an ultraviolet polymer formed on each of the surfaces on the liquid crystal layer side, the pixel electrode has a reflective electrode that reflects visible light, and the reflective electrode transmits ultraviolet light It is characterized by doing.

  In one embodiment, the reflective electrode includes a transparent conductive film and a dielectric multilayer film laminated with the transparent conductive film.

  In one embodiment, the reflective electrode has a transparent conductive film and a translucent film made of a metal thin film laminated with the transparent conductive film.

  In one embodiment, the pixel electrode further includes a transparent electrode, and the transparent electrode is formed of the same film as the transparent conductive film.

  In one embodiment, at least one opening provided only in the counter electrode of the pixel electrode and the counter electrode, and at least one opening disposed so as to overlap a polarization axis of the pair of polarizing plates. It has a cross-shaped opening.

  In one embodiment, the pixel electrode further includes a transparent electrode, and the at least one cross-shaped opening includes an opening disposed at a position facing each of the reflective electrode and the transparent electrode.

  In one embodiment, the ultraviolet polymer includes a monomer polymer of either diacrylate or dimethacrylate, and the liquid crystal layer includes the monomer.

  In one embodiment, the pair of orientation maintaining layers includes particles of the ultraviolet polymer having a particle size of 50 nm or less.

  Since the liquid crystal display device of the present invention has a reflective electrode that transmits ultraviolet light and reflects visible light, an alignment maintaining layer composed of an ultraviolet polymer can be formed on the reflective electrode using PSA technology. Therefore, the pretilt azimuth of the liquid crystal molecules on the reflective electrode can be regulated stably.

  The liquid crystal display device according to an embodiment of the present invention will be described below with reference to the drawings, but the present invention is not limited to the embodiment described below. Here, a reflection / transmission type (semi-transmission type) liquid crystal display device in which a pixel has a reflection region in which display is performed in the reflection mode and a transmission region in which transmission is performed in the transmission mode is illustrated. Needless to say, the present invention can be applied to a liquid crystal display device. In addition, here, among the VA mode liquid crystal display devices, the configuration in which the alignment is divided by the cross slit described in Patent Document 3 is illustrated, but the present invention is not limited to this, and the above-described MVA mode or CPA mode liquid crystal display devices are exemplified. It can also be applied to.

  With reference to FIG. 1 (a) and (b), the structure and operation | movement of the liquid crystal display device 100 of embodiment by this invention are demonstrated. The liquid crystal display device 100 is, for example, a TFT type liquid crystal display device having a plurality of pixels arranged in a matrix having rows and columns. FIG. 1 is a diagram schematically showing the structure of one pixel of the liquid crystal display device 100, FIG. 1 (a) is a plan view, and FIG. 1 (b) is a line 1B-1B ′ in FIG. 1 (a). It is typical sectional drawing in alignment with.

  The liquid crystal display device 100 has a pair of glass substrates 11 and 21 and a pair of polarizing plates (not shown) provided outside these and disposed in crossed Nicols, and displays a liquid crystal display in a normally black mode. Device. Each pixel has a liquid crystal layer 42 containing a nematic liquid crystal material (liquid crystal molecules 42 a) having a negative dielectric anisotropy, and a pixel electrode 14 and a counter electrode 24 facing each other with the liquid crystal layer 42 interposed therebetween. A pair of vertical alignment films 32 a and 32 b are provided between the pixel electrode 14 and the liquid crystal layer 42 and between the counter electrode 24 and the liquid crystal layer 42. Further, a pair of alignment maintaining layers 34a and 34b made of an ultraviolet polymer are formed on the surfaces of the alignment films 32a and 32b on the liquid crystal layer 42 side, respectively. The thickness of the liquid crystal layer 42 is defined by the spacer 44. Although simplified in the figure, the spacer 44 is covered with the vertical alignment film 32b.

  As shown in FIG. 1A, the pixel electrode 14 included in the liquid crystal display device 100 includes a reflective electrode 14R that reflects visible light and a transparent electrode 14T that transmits visible light. The reflective electrode 14R and the transparent electrode 14T is arranged in a line. The pixel electrode 14 includes a transparent conductive film 14 a and a dielectric multilayer film 15. The dielectric multilayer film 15 is laminated with a part 14r of the transparent conductive film 14a, and the dielectric multilayer film 15 and the transparent conductive film 14r constitute a reflective electrode 14R. The other part 14t of the transparent conductive film 14a constitutes a transparent electrode 14T. The reflective electrode 14R defines a reflective region R for displaying in the reflective mode, and the transparent electrode 14T defines a transmissive region T for displaying in the transmissive mode (see FIG. 1B).

  A portion 14r constituting the reflective electrode 14R and a portion 14t constituting the transparent electrode 14T of the transparent conductive film 14a are connected by a bridge portion 14b. In other words, a notch is provided between the transparent conductive films 14r and 14t so that the transparent conductive film 14r and the transparent conductive film 14t are substantially rectangular. By making the outer shape of the pixel electrode 14 like this, an oblique electric field generated at the edge portion of the pixel electrode 14 acts to stably form a 4D structure in each of the reflective region R and the transmissive region T. To do.

  The dielectric multilayer film 15 is configured to transmit ultraviolet light having a specific wavelength used in the ultraviolet polymerization reaction for generating the ultraviolet polymer constituting the alignment maintaining layers 34a and 34b, and to reflect visible light. Yes. In general, the wavelength of ultraviolet rays used to cure the ultraviolet curable resin is 365 nm (i-line), and it is preferable to transmit 50% or more of the ultraviolet rays. The higher the transmittance of ultraviolet rays, the better. When the transmittance is less than 50%, there is a problem that the time for irradiating ultraviolet rays becomes long and the throughput decreases. Further, in the orientation maintaining layer 34a, the state of the orientation maintaining layer 34a differs between the portion formed on the reflective electrode 14R and the portion formed on the transparent electrode 14T, and the display quality may deteriorate. .

As is well known, the dielectric multilayer film 15 is produced by alternately multilayering dielectrics having different refractive indexes. Examples of the dielectric material having a high refractive index include TiO ₂ and ZnO ₂ , and examples of the material having a low refractive index include SiO ₂ . An optical filter having a dielectric multilayer film that transmits ultraviolet light and reflects visible light and infrared light is commercially available as a UV cold filter.

  Since the dielectric multilayer film 15 does not have conductivity, if it is disposed on the liquid crystal layer 42 side of the transparent conductive film 14r, the voltage applied to the liquid crystal layer 42 drops. You may form in the other side (lower side in a figure). At this time, it is preferable to match the voltage-transmittance characteristic of the reflection region R and the voltage-transmittance characteristic of the transmission region T by adjusting the thickness of the liquid crystal layer 42 in the reflection region R.

  In place of the dielectric multilayer film 15, a translucent film made of a metal (Al, Ag, etc.) thin film may be used. The translucent film does not depend on the wavelength, that is, partially transmits and reflects partially from ultraviolet light to visible light. Since the metal thin film has conductivity, the translucent film 15 only needs to be electrically connected to the transparent conductive film 14t, and the transparent conductive film 14r can be omitted. ITO or IZO can be used as the transparent conductive film 14a. Since the ultraviolet transmittance of ITO is, for example, about 40%, the ultraviolet transmittance of the translucent film is preferably in the range of about 20% to about 80%.

  Even if slits and openings are formed in the metal film instead of the semitransparent film 15, the alignment maintaining layer 34a can be formed on the liquid crystal layer 42 side of the reflective electrode 14R. However, the alignment maintaining layer 34a formed in this manner is not preferable because it becomes non-uniform on the reflective electrode 14R and cannot exhibit a stable alignment regulating force. Therefore, as described above, it is preferable to form it uniformly (without providing slits or openings) on the entire surface of the reflective region R, such as the dielectric multilayer film 15 or the translucent film.

  A color filter layer 22, a transparent resin layer 23, and a counter electrode 24 are formed on the glass substrate 21 disposed on the viewer side. The color filter layer 22 may have a light shielding portion (black matrix) between the pixels as necessary. As described above, since the color filter layer 22 is generally provided on the substrate 21 on the viewer side, the liquid crystal layer 42 is formed even when the ultraviolet rays for forming the alignment maintaining layers 34a and 34b are irradiated from the substrate 21 side. Therefore, it is necessary to irradiate ultraviolet rays from the substrate 11 side. A method for forming the alignment maintaining layers 34a and 34b will be described later.

  The counter electrode 24 has cross-shaped openings 24a1 and 24a2. The opening 24a1 corresponds to the transmission region T, and the opening 24a2 is provided to correspond to the reflection region R. A 4D structure is formed in each of the transmissive region T and the reflective region R by the oblique electric field generated in the edge portion of the pixel electrode 14 and the oblique electric field generated in the vicinity of the openings 24a1 and 24a2 of the counter electrode 24. The alignment maintaining layers 34a and 34b function to maintain (store) the alignment of the liquid crystal molecules 42a in a state where a voltage is applied to the liquid crystal layer 42 even after the voltage is removed (a state where no voltage is applied). Accordingly, the pretilt azimuth of the liquid crystal molecules 42a defined by the alignment maintaining layers 34a and 34b (the tilt azimuth of the liquid crystal molecules when no voltage is applied) is the orientation of the director of the domain of the 4D structure formed when the voltage is applied. Align. Polarization axes of polarizing plates (not shown) arranged in crossed Nicols are arranged in parallel (overlapping) with the crosses of the openings 24a1 and 24a2. That is, the polarization axis of one polarizing plate is arranged in the horizontal direction, and the other polarizing axis is arranged in the vertical direction. Therefore, the orientations of the directors of the four liquid crystal domains formed in each of the reflection region R and the transmission region T are approximately 45 degrees with respect to the polarization axes of the pair of polarizing plates.

  The liquid crystal display device 100 has a transparent resin layer 23 in the reflection region R. When the same voltage is applied to the liquid crystal layer 42 in the reflective region R and the liquid crystal layer 42 in the transmissive region T, the optical path length for the light for displaying in the reflective mode and the optical path length for the light for displaying in the transmissive mode are made equal. In addition, the thickness of the liquid crystal layer 42 in the reflective region R is preferably half of the thickness of the liquid crystal layer 42 in the transmissive region T. The transparent resin layer 23 is provided for adjusting the thickness of the liquid crystal layer 42. Moreover, when the reflective electrode 14R has a flat reflective surface (mirror surface) as exemplified here, the transparent resin layer 23 may be provided with a light diffusion (scattering) function.

  As described above, since the liquid crystal display device 100 of the present embodiment uses a combination of the 4D structure and linearly polarized light, the transmission is higher than that of a conventional CPA mode liquid crystal display device using a quarter wavelength plate. Ratio, high contrast ratio and wide viewing angle characteristics. Furthermore, since the pretilt azimuth is defined so as to match the 4D structure even when no voltage is applied, the alignment of liquid crystal molecules is stabilized even at a lower gradation than the liquid crystal display device described in Patent Document 3. Of course, it has a characteristic that the response characteristic is excellent as in the case of a conventional liquid crystal display device subjected to PSA processing.

  The liquid crystal display device 100 is, for example, a TFT-type liquid crystal display device, and includes a TFT, a gate bus line, a source bus line, and an interlayer insulating film that covers these (not shown). The TFT is ON / OFF controlled by a scanning signal supplied to the gate bus line, and a display signal is supplied from the source bus line to the pixel electrode when the TFT is in the ON state. By providing an interlayer insulating film formed of a transparent organic resin, the edge portion of the pixel electrode can be overlaid on the source bus line, so that the pixel aperture ratio can be improved. Further, by forming irregularities on the surface of the interlayer insulating film present in the reflective region R and forming the reflective electrode 14R thereon, it is possible to impart diffuse reflection characteristics to the reflective electrode 14R. In this way, it is not necessary to impart diffusion characteristics to the transparent resin layer 23.

  The orientation maintaining layers 34a and 34b are formed using the PSA technique, and specific manufacturing methods are described in Patent Documents 4 and 5. Here, a liquid crystal panel was produced in the same manner as described in Patent Document 5 (Example 5).

  A liquid crystal display panel for the liquid crystal display device 100 is manufactured using a material in which a photopolymerizable monomer of 0.1% by mass to 0.5% by mass is mixed with a nematic liquid crystal material having a negative dielectric anisotropy. To do. As the photopolymerizable monomer, a diacrylate or dimethacrylate monomer having a liquid crystal skeleton is used. The liquid crystal display panel has substantially the same configuration as the liquid crystal display device 100 except that the liquid crystal material contains a monomer, the alignment maintaining layers 34a and 34b are not formed, and the polarizing plate is not provided. I have.

In a state where a voltage (10 V) higher than a white display voltage (for example, 4.5 V) is applied to the liquid crystal layer (including the monomer) of the liquid crystal display panel, UV light (for example, i having a wavelength of 365 nm is applied from the substrate 11 side). Line, about 5.8 mW / cm < ² >) for about 3-5 minutes. When a sufficiently large voltage is applied to the liquid crystal layer, the director has an azimuth angle of 45 degrees in the liquid crystal layer due to the electric field generated between the counter electrode 24 having the cross-shaped openings 24a1 and 24a2 and the pixel electrode 14. Four domains of 135 degrees, 225 degrees and 315 degrees are formed. Monomer is polymerized by UV light irradiation to produce an ultraviolet polymer. The ultraviolet polymer forms alignment maintaining layers 34a and 34b for fixing the alignment state of the liquid crystal molecules 42a on the vertical alignment films 32a and 32b. Since the reflective electrode 14R transmits UV light, the orientation maintaining layer 34a is also formed on the reflective electrode 14R. Thereafter, in order to reduce monomers remaining in the liquid crystal layer 42, UV light is further irradiated. For example, about 1.4 mW / cm ² of UV light is irradiated for about 1 to 2 hours using a black light. A series of these processes may be referred to as “PSA processing”.

  The structure of one example of the alignment sustaining layers 34a and 34b will be described with reference to FIG. The SEM image shown in FIG. 2 is obtained by observing the surface of the liquid crystal display panel manufactured as described above after disassembling, removing the liquid crystal material, and washing with a solvent.

  As can be seen from FIG. 2, the orientation maintaining layer contains ultraviolet polymer particles having a particle size of 50 nm or less. The ultraviolet polymer does not necessarily cover the entire surface of the alignment film, and a part of the surface of the alignment film may be exposed. Liquid crystal molecules aligned in accordance with the electric field formed in the liquid crystal layer are fixed by the ultraviolet polymer, and the alignment is maintained even in the absence of an electric field. After the alignment maintaining layer on the vertical alignment film is formed, the alignment maintaining layer defines the pretilt direction of the liquid crystal molecules.

  With reference to FIGS. 3 and 4, the function of the alignment sustaining layers 34a and 34b will be described. 3 corresponds to a cross-sectional view taken along line 1B-1B ′ in FIG. 1 with respect to the reflective region R or transmissive region T of the liquid crystal display device 100 of the embodiment, and FIG. 3A is a black display state (no voltage applied). 3B shows the alignment state of the liquid crystal molecules 42a in the white display state (when voltage is applied). An opening provided in the counter electrode 24 is shown as an opening 24a.

  On the other hand, FIG. 4 is a cross-sectional view of a pixel of the liquid crystal display device (corresponding to the liquid crystal display device 100 from which the alignment maintaining layers 34a and 34b are removed) described in Patent Document 3, and FIG. FIG. 4B shows the alignment state of the liquid crystal molecules 42a in the black display state (when no voltage is applied) and in the white display state (when voltage is applied). In FIGS. 3 and 4, the vertical alignment films 32a and 32b are omitted.

  First, FIG. 4 will be referred to for explaining the alignment of the liquid crystal molecules 42a by the oblique electric field. As shown in FIG. 4A, when no voltage is applied, the liquid crystal molecules 42a are vertically aligned by a vertical alignment film (not shown). On the other hand, in the white display state, the orientation direction of the liquid crystal molecules 42 a is defined by the oblique electric field generated at the edge portion of the pixel electrode 14 and the oblique electric field generated near the opening 24 a of the counter electrode 24. The liquid crystal molecules 42a near the center of the liquid crystal layer 42 are aligned so that the major axis of the molecules is perpendicular to the electric field (since the dielectric anisotropy is negative). When viewed from the normal direction of the liquid crystal layer 42, four domains having director azimuth angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees are formed, so that the twist is centered on the opening 24a. Accordingly, in FIG. 4B, the liquid crystal molecules 42a in the region corresponding to the opening 24a are aligned in a direction perpendicular to the paper surface. Since the liquid crystal molecules 42a closest to the vertical alignment film (not shown) are strongly anchored by the vertical alignment film, they are aligned perpendicular to the surface of the vertical alignment film even in the white display state. Yes.

  Next, refer to FIGS. 3A and 3B. The liquid crystal display device 100 includes alignment maintaining layers 34a and 34b, and the alignment maintaining layers 34a and 34b act to fix the alignment of the liquid crystal molecules 42a when an electric field is applied. That is, when the liquid crystal molecules 42a are aligned as shown in FIG. 3B, the monomers are polymerized as described above to form the alignment maintaining layers 34a and 34b, and the alignment at this time is fixed. Has been.

  As shown in FIG. 3B, since the liquid crystal molecules 42a closest to the vertical alignment film are subjected to strong anchoring action, an applied voltage at the time of light irradiation (for example, 10V higher than the white display voltage). Is approximately perpendicular to the surface of the vertical alignment film. Accordingly, the liquid crystal molecules 42a fixed by the alignment maintaining layers 34a and 34b formed on the vertical alignment film are inclined slightly (1 to 5 °) from the vertical direction as schematically shown in FIG. Liquid crystal molecules 42a fixed by the alignment maintaining layers 34a and 34b, as can be seen by comparing FIG. 3A and FIG. 3B. The orientation of the film hardly changes even when a voltage is applied.

  Since the liquid crystal display device 100 of the embodiment according to the present invention has the alignment maintaining layers 34a and 34b, as shown in FIG. 3A, the liquid crystal display device 100 exhibits an alignment state pretilted in a predetermined direction even when no voltage is applied. The alignment state at this time is consistent with the alignment state of the liquid crystal molecules 42a in the white display state (when voltage is applied) shown in FIG. 3B, and as a result, the alignment of the liquid crystal molecules is stable even at a low gradation. The advantage is that Further, in the liquid crystal display device 100, since the same orientation maintaining layer as that on the transmission electrode 14T is formed on the reflective electrode 14R, the pretilt direction of the liquid crystal molecules 42a on the reflective electrode 14R is also stably defined.

  The present invention is used in a liquid crystal display device that displays in a reflection mode, such as a liquid crystal display device for a cellular phone.

It is a figure which shows typically the structure of one pixel of the liquid crystal display device 100 of embodiment by this invention, Fig.1 (a) is a top view, FIG.1 (b) is 1B- of Fig.1 (a). It is typical sectional drawing along a 1B 'line. It is a figure which shows the SEM image of the orientation maintenance layer which the liquid crystal display device 100 of embodiment by this invention has. The reflective region R or transmissive region T of the liquid crystal display device 100 corresponds to a cross-sectional view taken along the line 1B-1B ′ in FIG. 1, where (a) is a black display state (when no voltage is applied), and (b) is white. It is a figure which shows typically the orientation state of the liquid crystal molecule 42a of a display state (at the time of voltage application). FIG. 4 is a cross-sectional view of a pixel of a liquid crystal display device described in Patent Document 3, wherein (a) is a black display state (when no voltage is applied), and (b) is a liquid crystal molecule 42a in a white display state (when a voltage is applied). It is a figure which shows an orientation state typically.

Explanation of symbols

11, 21 Substrate 14 Pixel electrode 14a Transparent conductive film 14b Bridge portion 14r Part of the transparent conductive film (part constituting the reflective electrode)
14R Reflective electrode 14t Part of the transparent conductive film (part constituting the transparent electrode)
14T transparent electrode 15 dielectric multilayer film 22 color filter layer 23 transparent resin layer 24 counter electrode 24a, 24a1, 24a2 cross-shaped opening (slit)
32a, 32b Vertical alignment film 34a, 34b Alignment maintaining layer 42 Liquid crystal layer 42a Liquid crystal molecule 44 Spacer 100 Liquid crystal display device

Claims (8)

A liquid crystal display device having a plurality of pixels,
Each of the plurality of pixels is
A liquid crystal layer comprising a nematic liquid crystal material having a negative dielectric anisotropy;
A pixel electrode and a counter electrode facing each other through the liquid crystal layer;
A pair of vertical alignment films provided between the pixel electrode and the liquid crystal layer and between the counter electrode and the liquid crystal layer;
A pair of alignment maintaining layers composed of an ultraviolet polymer formed on each of the liquid crystal layer side surfaces of the pair of vertical alignment films,
The pixel electrode includes a reflective electrode that reflects visible light, the reflective electrode transmits ultraviolet light, and one of the pair of alignment maintaining layers is formed on the liquid crystal layer side of the reflective electrode. apparatus.   The liquid crystal display device according to claim 1, wherein the reflective electrode includes a transparent conductive film and a dielectric multilayer film laminated with the transparent conductive film.   The liquid crystal display device according to claim 1, wherein the reflective electrode includes a transparent conductive film and a semitransparent film formed of a metal thin film laminated with the transparent conductive film.   The liquid crystal display device according to claim 2, wherein the pixel electrode further includes a transparent electrode, and the transparent electrode is formed of the same film as the transparent conductive film.   At least one opening provided only in the counter electrode of the pixel electrode and the counter electrode, and at least one cross-shaped opening disposed so as to overlap the polarization axis of the pair of polarizing plates The liquid crystal display device according to claim 1, comprising: The pixel electrode further includes a transparent electrode,
The liquid crystal display device according to claim 5, wherein the at least one cross-shaped opening includes an opening disposed at a position facing each of the reflective electrode and the transparent electrode.   The liquid crystal display device according to claim 1, wherein the ultraviolet polymer includes a monomer polymer of either diacrylate or dimethacrylate, and the liquid crystal layer includes the monomer.   The liquid crystal display device according to claim 1, wherein the pair of alignment maintaining layers includes particles of the ultraviolet polymer having a particle size of 50 nm or less.