JP2005107277A - Liquid crystal display element - Google Patents

Abstract

[PROBLEMS] To obtain a high-contrast display with a wide viewing angle, and to display both a color image display by reflection display using external light and a color image display by transmission display using illumination light from a light source. It can be done and both color images are displayed in a sufficiently bright quality with little difference.
SOLUTION: A pair of substrates 2, 3, pixel forming electrodes 4, 5 provided on the inner surfaces of these substrates, and color filters 6R, 6G, 6B provided corresponding to a plurality of pixels A, respectively. Reflecting means 8 provided on the opposite substrate 3 for dividing the plurality of pixels A into a reflective display portion A1 and a transmissive display portion A2, and liquid crystal molecules 12a are vertically aligned with respect to the substrate surface and sealed. A liquid crystal layer 12 made of a liquid crystal material having a negative dielectric anisotropy, wherein the layer thickness d1 of the reflective display portion A1 of the pixel A is smaller than the layer thickness d2 of the transmissive display portion A2, and the observation side and the opposite side A pair of polarizing plates 14 and 15 and two λ / 4 plates 16 and 17 disposed between the pair of substrates 2 and 3 and the polarizing plates 14 and 15 were provided.
[Selection] Figure 1

Description

  The present invention relates to a liquid crystal display element.

  As the liquid crystal display element, electrodes for forming a plurality of pixels are provided on the opposing inner surfaces of a pair of substrates on the observation side and the opposite side, which are opposite to each other, and a liquid crystal is provided between the pair of substrates. A liquid crystal layer made of a liquid crystal material having a positive dielectric anisotropy in which molecules are twisted in a state of lying substantially horizontally with respect to the substrate surface is provided, and is observed facing each of the outer surfaces of the pair of substrates. A TN (twisted nematic) type in which a pair of polarizing plates on the side and the opposite side is disposed is widely used (see Patent Document 1).

This TN type liquid crystal display element displays an image by controlling the polarization state of incident light by the birefringence of the liquid crystal layer. In a normally white mode liquid crystal display element, liquid crystal molecules are initially placed between the electrodes of the pixel. When an OFF voltage for aligning in the twist alignment state is applied, incident light is rotated by the liquid crystal layer and transmitted through the observation side polarizing plate, and the display of the pixel becomes bright display, and the liquid crystal molecules are interposed between the electrodes of the pixel. When an ON voltage is applied to rise and align the substrate substantially perpendicularly to the substrate surface, the light transmitted through the liquid crystal layer is absorbed by the observation side polarizing plate, and the pixel display becomes a dark display.
JP 11-007048 A

  However, the TN liquid crystal display element has a narrow viewing angle because the liquid crystal molecules are twisted with the liquid crystal molecules lying down substantially horizontally with respect to the substrate surface.

  In the TN type liquid crystal display element, the liquid crystal molecules in the vicinity of the substrate are strongly subjected to the alignment regulating force by the horizontal alignment film, and even when the ON voltage is applied, the ON voltage is hardly applied. In this case, the liquid crystal layer has residual retardation. Therefore, the normally white mode TN liquid crystal display element has insufficient darkness for dark display and low display contrast.

  The present invention has a wide viewing angle, can provide a high contrast display, and is disposed on the opposite side of the observation side from the color image display by the reflective display using the external light that is the light of the external environment. Liquid crystal capable of displaying both color images by transmissive display using illumination light from a light source, and displaying both color images with sufficiently bright quality with almost no difference. The object is to provide a display element.

  The liquid crystal display element of the present invention includes a pair of substrates facing each other on the observation side and the opposite sides thereof, electrodes provided on the opposing inner surfaces of the pair of substrates, and forming a plurality of pixels by regions facing each other A color filter of three colors of red, green, and blue provided corresponding to each of the plurality of pixels on one inner surface of the pair of substrates, and provided on the opposite substrate, and each of the plurality of pixels is Between the pair of substrates, a reflection means that divides the light incident from the observation side into a reflective display portion that reflects the light incident on the observation side and a transmissive display portion that transmits the light incident from the opposite side to the observation side, and a liquid crystal Dielectric anisotropy is formed in which molecules are encapsulated with the substrate oriented substantially perpendicular to the substrate surface, and the layer thickness of the reflective display portion of the plurality of pixels is smaller than the layer thickness of the transmissive display portion. From negative liquid crystal material A liquid crystal layer, an observation side disposed opposite to the outer surfaces of the pair of substrates, and a pair of polarizing plates on the opposite side, and between the pair of substrates and the pair of polarizing plates, at least for observation And a single λ / 4 plate disposed between the side substrate and the polarizing plate.

  In the liquid crystal display element according to the present invention, the substrate gap of the reflective display unit is made larger than the substrate gap of the transmissive display unit of the pixel so as to correspond to the reflective display unit of the plurality of pixels on one inner surface of the pair of substrates. It is preferable to provide a transparent film for reducing the thickness.

  In this liquid crystal display element, it is preferable that a vertical alignment film is formed on the inner surfaces of the pair of substrates, and the inner surfaces are rubbed in directions parallel to each other.

  Further, in the liquid crystal display element, the reflecting means for dividing the plurality of pixels into a reflective display portion and a transmissive display portion, respectively, includes a plurality of reflective films provided corresponding to the reflective display portion for each of the plurality of pixels. It is preferable that irregularities are formed on the reflective surfaces of these reflective films.

  The liquid crystal display element of the present invention includes at least an observation side birefringence effect of a liquid crystal layer provided between the observation side and a pair of substrates on the opposite side, and the pair of substrates and the pair of polarizing plates. The liquid crystal display element displays liquid crystal molecules on the substrate surface by controlling the polarization state of incident light by the phase difference of a λ / 4 plate disposed between the substrate and the polarizing plate. Wide viewing angle.

  In this liquid crystal display element, the liquid crystal layer is made of a liquid crystal material having negative dielectric anisotropy in which liquid crystal molecules are aligned substantially perpendicular to the substrate surface. When the OFF voltage is applied, the liquid crystal molecules are aligned in the initial vertical alignment state, and when the ON voltage is applied, the alignment state is such that all the liquid crystal molecules between the pair of substrates are inclined with respect to the substrate surface. Change.

  Therefore, according to this liquid crystal display element, when an OFF voltage for aligning liquid crystal molecules in the initial vertical alignment state is applied between the electrodes of the pixel, incident light is hardly subjected to birefringence on the liquid crystal layer. The ON state voltage is controlled so that the polarization state is controlled by the phase difference of the λ / 4 plate to be incident on the polarizing plate on the observation side, and the liquid crystal molecules are tilted between the electrodes of the pixel with respect to the substrate surface. When applied, incident light can be incident on the polarizing plate on the observation side by controlling the polarization state by the birefringence action of the liquid crystal layer and the phase difference of the λ / 4 plate, and thus has high contrast. Can be obtained.

  In addition, the liquid crystal display element is provided with three color filters of red, green, and blue corresponding to the plurality of pixels on one inner surface of the pair of substrates, and on the substrate opposite to the observation side. And a reflecting means for dividing the plurality of pixels into a reflective display portion that reflects light incident from the observation side to the observation side and a transmissive display portion that transmits light incident from the opposite side to the observation side. Therefore, both color image display by reflection display using external light, which is light from the external environment, and color image display by transmission display using illumination light from the light source arranged on the side opposite to the observation side Can be displayed.

  In this liquid crystal display element, since the reflecting means for dividing the plurality of pixels into the reflective display portion and the transmissive display portion is provided on the substrate on the side opposite to the observation side, the reflective display using the external light is provided. In this case, light absorption by the polarizing plate is only absorption by the polarizing plate on the observation side, and therefore the color image by the reflection display can be sufficiently brightened.

  Further, since the liquid crystal layer thickness of the reflective display unit of the plurality of pixels is smaller than the liquid crystal layer thickness of the transmissive display unit, the liquid crystal display element reciprocates the liquid crystal layer of the reflective display unit. The difference between the birefringence effect of the liquid crystal layer with respect to the transmitted light and the birefringence effect of the liquid crystal layer with respect to the light transmitted only once through the liquid crystal layer of the transmissive display unit is reduced, and the color image and the transmission by the reflective display Both the displayed color image and the quality can be displayed with almost no difference.

  In the liquid crystal display element according to the present invention, the substrate gap of the reflective display unit is made larger than the substrate gap of the transmissive display unit of the pixel so as to correspond to the reflective display unit of the plurality of pixels on one inner surface of the pair of substrates. It is preferable to provide a transparent film for reducing the thickness of the liquid crystal layer. In this way, the liquid crystal layer thickness of the reflective display portion of the plurality of pixels is smaller than the liquid crystal layer thickness of the transmissive display portion with a simple structure. can do.

  Further, in this liquid crystal display element, it is preferable that a vertical alignment film is formed on the inner surfaces of the pair of substrates, and the inner surfaces are rubbed in directions parallel to each other. By defining the collapse direction of the liquid crystal molecules when a voltage is applied to the direction along the rubbing direction, higher contrast can be obtained.

  Further, in the liquid crystal display element, the reflecting means for dividing the plurality of pixels into a reflective display portion and a transmissive display portion, respectively, includes a plurality of reflective films provided corresponding to the reflective display portion for each of the plurality of pixels. It is preferable that the reflective surfaces of these reflective films have irregularities. By doing so, the reflective display can be brightened and the viewing angle can be widened.

  1 to 5 show a first embodiment of the present invention, and FIG. 1 is a sectional view of a part of a liquid crystal display element.

  As shown in FIG. 1, the liquid crystal display element of this embodiment includes a liquid crystal element 1, a pair of polarizing plates 14 and 15 on the observation side and the opposite side disposed with the liquid crystal element 1 interposed therebetween, and the liquid crystal Two λ / 4 plates 16 and 17 disposed between the pair of substrates 2 and 3 of the element 1 and the pair of polarizing plates 14 and 15, respectively, and the observation side substrate 2 and the observation side of the liquid crystal element 1 And a diffusion layer 18 provided between the λ / 4 plate 16.

  The liquid crystal element 1 includes a pair of transparent substrates 2 and 3 on the observation side (upper side in FIG. 1) facing each other and the opposite side (lower side in FIG. 1), and inner surfaces facing the pair of substrates 2 and 3, respectively. Transparent electrodes 4 and 5 that form a plurality of pixels A by regions facing each other, and correspond to the plurality of pixels A on one of the pair of substrates 2 and 3, for example, the inner surface of the observation-side substrate 2 The red, green, and blue color filters 6R, 6G, and 6B provided on the inner surface of the substrate 3 on the opposite side, and light incident on the plurality of pixels A from the observation side, respectively. Between the pair of substrates 2 and 3, liquid crystal molecules are divided between the reflection means 8 that divides the reflection display portion A 1 that reflects to the observation side and the transmissive display portion A 2 that transmits light incident from the opposite side to the observation side. 12a with respect to the substrate 2 and 3 surfaces A liquid crystal having a negative dielectric anisotropy, which is sealed in a substantially vertical orientation and is formed such that the layer thickness d1 of the reflective display portion A1 of the plurality of pixels A is smaller than the layer thickness d2 of the transmissive display portion A2. The liquid crystal layer 12 is made of a material.

  This liquid crystal element 1 is provided with a single film-like counter electrode 4 on the inner surface of the observation side substrate 2 and a plurality of pixel electrodes 5 arranged in a matrix in the row and column directions on the inner surface of the opposite substrate 3. The plurality of pixel electrodes 5 are respectively connected to a plurality of TFTs 7 provided on the inner surface of the opposite substrate 3.

  Although the TFT 7 is shown in a simplified manner in FIG. 1, the TFT 7 is formed on a substantially entire surface of the substrate 3 so as to cover the gate electrode formed on the opposite substrate 3 and the gate electrode. A transparent gate insulating film; an i-type semiconductor film formed on the gate insulating film so as to face the gate electrode; and an n-type semiconductor film on both sides of the i-type semiconductor film. Source electrode and drain electrode.

  Although omitted in FIG. 1, a plurality of gate wirings for supplying gate signals to the TFTs 7 in each row and a plurality of data wirings for supplying data signals to the TFTs 7 in each column are provided on the inner surface of the opposite substrate 3. The gate wiring is formed integrally with the gate electrode of the TFT 7 on the substrate surface of the opposite substrate 3 and covered with the gate insulating film, and the data wiring is formed on the gate insulating film. Formed and connected to the drain electrode of the TFT 7.

  Reflecting means 8 for dividing the plurality of pixels A into a reflective display portion A1 and a transmissive display portion A2 respectively corresponds to the reflective display portion A1 for each of the plurality of pixels A on the gate insulating film. A plurality of specular reflection films 8 a are provided, and the plurality of pixel electrodes 5 are formed on the gate insulating film with a part of the plurality of pixel electrodes 5 superimposed on the reflection film 8 a and connected to the source electrode of the TFT 7. Has been.

  In this embodiment, the reflective film 8a is provided so as to correspond to a substantially half area of the pixel A, the substantially half area of the plurality of pixels A is used as the reflective display portion A1, and the other substantially half area is formed. The transmissive display portion A2 is used.

  On the other hand, the three color filters 6R, 6G, 6B of red, green, and blue provided on the inner surface of the observation side substrate 2 are formed on the substrate surface of the observation side substrate 2, and these color filters 6R, Substrates for making the substrate gap of the reflective display portion A1 smaller than the substrate gap of the transmissive display portion A2 of the pixel A in correspondence with the reflective display portions A1 of the plurality of pixels A on 6G and 6B. A gap adjusting transparent film 9 is provided.

  Each of the color filters 6R, 6G, and 6B is provided with an opening that partially corresponds to the reflective display portion A1 of the pixel A. The substrate gap adjusting transparent film 9 includes the color filters 6R, 6R, and 6B. 6G and 6B are filled in the openings. In this embodiment, the openings of the color filters 6R, 6G, 6B are formed so as to correspond to substantially half of the area of the reflective display portion A1.

  The counter electrode 4 is formed on the color filters 6R, 6G, 6B and the substrate gap adjusting transparent film 9.

  Further, vertical alignment films 10 and 11 are formed on the inner surfaces of the observation-side substrate 2 and the opposite-side substrate 3 so as to cover the electrodes 4 and 5, respectively. The film surfaces of the alignment films 10 and 11 are rubbed in directions parallel to each other.

  The observation side substrate 2 and the opposite side substrate 3 are joined via a frame-shaped sealing material (not shown) surrounding a display area in which the plurality of pixels A are arranged in a matrix. A liquid crystal layer 12 is formed by filling a liquid crystal material having a negative dielectric anisotropy, for example, a nematic liquid crystal having a negative dielectric anisotropy, in a region surrounded by the sealing material between the three.

  The liquid crystal molecules 12a of the liquid crystal layer 12 are aligned substantially perpendicular to the pair of substrates 2 and 3, and when an ON voltage is applied between the electrodes 4 and 5 of the plurality of pixels A, With respect to the surfaces of the substrates 2 and 3, the molecules are aligned in a tilted manner with the molecular long axes aligned in the direction along the rubbing direction.

  In this embodiment, the reflective film 9 for adjusting the substrate gap is formed so that the substrate gap of the reflective display portion A1 is approximately half the substrate gap of the transmissive display portion A2. The liquid crystal layer thickness d1 of the display portion A1 is made approximately ½ of the liquid crystal layer thickness d2 of the transmissive display portion A2, and the values of the liquid crystal layer thicknesses d1 and d2 and the refractive index anisotropy Δn of the liquid crystal material are set. By selecting, Δnd1 of the reflective display portion A1 and Δnd2 of the transmissive display portion A2 when the ON voltage is applied, that is, when the liquid crystal molecules 12a are aligned with the molecular long axis aligned in the rubbing direction are Δnd1 = 140 ± 40 nm and Δnd2 = 270 ± 40 nm.

  The pair of polarizing plates 14 and 15 on the observation side and the opposite side are absorption polarizing plates each having a transmission axis and an absorption axis in directions orthogonal to each other, and the observation-side polarizing plate 14 is used for observing the liquid crystal element 1. The opposite side polarizing plate 15 is disposed opposite to the outer surface of the opposite substrate 3 of the liquid crystal element 1.

  Each of the two λ / 4 plates 16 and 17 is a phase difference plate that gives a phase difference of ¼ wavelength (140 ± 40 nm) between the ordinary light and the extraordinary light of the transmitted light. A λ / 4 plate (hereinafter referred to as an observation side λ / 4 plate) 16 is disposed between the observation side substrate 2 of the liquid crystal element 1 and the observation side polarizing plate 14, and the other λ / 4 plate (hereinafter referred to as an λ / 4 plate). The opposite side λ / 4 plate) 17 is disposed between the opposite side substrate 3 of the liquid crystal element 1 and the opposite side polarizing plate 15.

  2 shows the rubbing directions 2a and 3a of the inner surfaces of the pair of substrates 2 and 3 of the liquid crystal element 1 (the film surfaces of the vertical alignment films 10 and 11) and the transmission axes 14a of the polarizing plates 14 and 15 on the observation side and the opposite side. , 15a and the directions of the slow axes 16a, 17a of the λ / 4 plates 16, 17 on the observation side and the opposite side.

  As shown in FIG. 2, the inner surfaces of the pair of substrates 2 and 3 of the liquid crystal element 1 are rubbed in parallel and in opposite directions, and the observation-side polarizing plate 14 has its transmission axis 14a aligned with the pair of substrates. The substrates 2 and 3 are arranged so as to obliquely intersect with the rubbing directions 2a and 3a of the inner surfaces of the substrates 2 and 3 at an angle of substantially 45 °, and the opposite side polarizing plate 15 has its transmission axis 15a aligned with the observation side polarizing plate 14. It is arranged so as to be substantially orthogonal to the transmission axis 14a.

  The observation side λ / 4 plate 16 has its slow axis 16a substantially orthogonal to or substantially parallel to the rubbing directions 2a and 3a of the inner surfaces of the pair of substrates 2 and 3, so that the observation side The opposite side λ / 4 plate 17 is arranged obliquely intersecting the transmission axis 14a of the polarizing plate 14 at an angle of substantially 45 °, and the opposite side λ / 4 plate 17 has its slow axis 17a as the observation side λ / 4 plate. 16 slow axes 16a are substantially orthogonal (practically parallel to or substantially orthogonal to the rubbing directions 2a and 3a of the inner surfaces of the pair of substrates 2 and 3), and are aligned with the transmission axis 15a of the opposite polarizing plate 15. On the other hand, they are arranged so as to cross obliquely at an angle of substantially 45 °.

  The diffusion layer 18 provided between the liquid crystal element 1 and the observation side λ / 4 plate 16 is a front diffusion layer that diffuses light incident from one surface and emits it from the other surface. The diffusion layer 18 is made of an adhesive or a resin film in which light diffusion particles are mixed.

  The liquid crystal display element includes a birefringence action of the liquid crystal layer 12 provided between the pair of substrates 2 and 3 on the observation side of the liquid crystal element 1 and the opposite side, the pair of substrates 2 and 3 and the observation side, and The liquid crystal display element is for controlling the polarization state of incident light based on the phase difference between the two λ / 4 plates 16 and 17 disposed between the polarizing plates 14 and 15 on the opposite side. Has a wide viewing angle because the liquid crystal molecules 12a of the liquid crystal layer 12 are aligned substantially perpendicular to the surfaces of the substrates 2 and 3.

  In the liquid crystal display element, the liquid crystal layer 12 is made of a liquid crystal material having a negative dielectric anisotropy in which the liquid crystal molecules 12a are aligned substantially perpendicular to the surfaces of the substrates 2 and 3, and Since the vertical alignment films 10 and 11 formed on the inner surfaces of the substrates 2 and 3 have a smaller alignment regulating force than the horizontal alignment film, when an OFF voltage is applied between the electrodes 4 and 5 of the pixel A, the liquid crystal molecules When 12a is aligned in the initial vertical alignment state and an ON voltage is applied, the alignment state is changed in a direction in which all liquid crystal molecules 12a between the pair of substrates 2 and 3 fall on the substrate surface.

  FIG. 3 is a schematic diagram showing the alignment state of the liquid crystal molecules 12a when the OFF voltage is applied and when the ON voltage is applied. In this embodiment, the inner surfaces of the pair of substrates 2 and 3 of the liquid crystal element 1 are parallel to each other and reversed. Since the liquid crystal molecules 12a are rubbed in the direction, the liquid crystal molecules 12a are applied with the ON voltage from the vertical alignment state when the OFF voltage is applied as shown in FIG. 3A, as shown in FIG. The substrate 2 and the surface 3 are aligned in a non-twisted homogeneous alignment state in which the molecular major axes are aligned in a direction along the rubbing directions 2a and 3a.

  Therefore, according to this liquid crystal display element, when an OFF voltage for aligning the liquid crystal molecules 12a in the initial vertical alignment state is applied between the electrodes 4 and 5 of the pixel A, the incident light is reflected in the liquid crystal layer 12. The light is transmitted almost without being refracted, and the state of polarization is controlled by the phase difference of one or both of the λ / 4 plates 16 and 17 so as to be incident on the observation side polarizing plate 14. 5, when an ON voltage is applied to cause the liquid crystal molecules 12 a to be in a tilted orientation with respect to the substrates 2 and 3, incident light is converted into birefringence of the liquid crystal layer 12 and one of the λ / 4 plates 16 and 17, or The polarization state is controlled by both phase differences and can be made incident on the observation-side polarizing plate 14, so that a high-contrast display can be obtained.

  In addition, this liquid crystal display element has three colors of red, green, and blue corresponding to the plurality of pixels A on one of the pair of substrates 2 and 3 of the liquid crystal element 1, for example, the inner surface of the observation side substrate 2. The reflective display unit A1 that provides the filters 6R, 6G, and 6B and reflects the light incident on the plurality of pixels A from the observation side to the observation side on the inner surface of the substrate 3 opposite to the observation side, and the Since the reflecting means 8 for dividing the light incident from the opposite side into the transmissive display portion A2 that transmits the light to the observation side is provided, color image display by reflection display using external light that is light of the external environment, and observation Both color image display and transmissive display using illumination light from the surface light source 19 arranged on the opposite side can be performed.

  The reflective display using the external light of the liquid crystal display element will be described. FIG. 4 is a schematic diagram of the reflective display of the liquid crystal display element, and shows the display of the reflective display portion A1 of one pixel A of the liquid crystal element 1. ing.

  4A shows a display when an OFF voltage for aligning the liquid crystal molecules 12a in the initial vertical alignment state is applied between the electrodes 4 and 5 of the pixel A, and FIG. 4B shows an electrode of the pixel A. 4 shows a display when an ON voltage is applied between 4 and 5 to cause the liquid crystal molecules 12a to be in a tilted orientation.

In the case of reflective display using external light, this liquid crystal display element is a single polarizer type display in which the observation side polarizing plate 14 disposed on the observation side of the liquid crystal element 1 serves as both a polarizer and an analyzer. In this reflective display, the external light a ₀ incident from the observation side is transmitted by the observation side polarizing plate 14 as indicated by the arrow in FIGS. 4 (a) and 4 (b). The liquid crystal layer 12 of the liquid crystal element 1 is linearly polarized light a ₁ parallel to the axis 14 a and further circularly polarized light a ₂ around the left or right when viewed from the traveling direction of the light by the observation side λ / 4 plate 16. Is incident on.

Then, when OFF voltage is applied, liquid crystal molecules 12a of the liquid crystal layer 12 is because it is substantially vertically oriented, has been circularly polarized light a ₂ by the observation side lambda / 4 plate 16 enters the liquid crystal layer 12 The light is transmitted through the liquid crystal layer 12 with almost no birefringence as it is with the circularly polarized light a ₂ , and the light is incident on the reflective display portion A 1 of the plurality of pixels A and is transmitted through the liquid crystal layer 12. light is reflected by the reflective film 8a, for emitting the liquid crystal layer 12 on the observation side of the liquid crystal element 1 as the circle and leave again transmitted polarized light a ₂ FIG 4 (a).

The circularly polarized light a ₂ emitted to the observation side of the liquid crystal element ₁ is substantially the same as the linearly polarized light a ₁ that is transmitted through the observation side polarizing plate 14 from the observation side and incident by the observation side λ / 4 plate 16. is a linearly polarized light a ₃ perpendicular incident on the observation side polarizing plate 14 is absorbed by the observation side polarizing plate 14, the display of the pixel a was applied to the OFF voltage becomes dark display black.

In addition, when the ON voltage is applied, the liquid crystal molecules 12a of the liquid crystal layer 12 are aligned with the major axis in the direction along the rubbing directions 2a and 3a of the substrates 2 and 3 as described above. The light that has been made circularly polarized light a ₂ by the side λ / 4 plate 16 and incident on the liquid crystal layer 12 changes its polarization state due to the birefringence of the liquid crystal layer 12, and the reflected display of the plurality of pixels A out of the light. The light that has entered the portion A1 and has passed through the liquid crystal layer 12 is reflected by the reflective film 8a, passes through the liquid crystal layer 12 again with its polarization state changed, and is emitted to the observation side of the liquid crystal element 1.

The birefringence action of the liquid crystal layer 12 of the reflective display portion A1 when the ON voltage is applied is that Δnd1 of the reflective display portion A1 when the liquid crystal molecules 12a are oriented in a tilted manner is 140 ± 40 nm as described above. Therefore, the light that has been made circularly polarized light a ₂ by the observation side λ / 4 plate 16 and incident on the liquid crystal layer 12 of the reflective display unit A 1 is transmitted by the liquid crystal layer 12. The linearly polarized light (not shown) that is substantially the same as the linearly polarized light a ₁ that has passed through the observation side polarizing plate 14 and entered from the observation side is reflected by the reflective film 8 a and is further reflected by the liquid crystal layer 12 on the observation side. lambda / 4 emitted through the plate 16 is circularly polarized light a ₂ incident on the liquid crystal layer 12 is rotation direction and opposite circular polarization a ₄ on the viewing side of the liquid crystal element 1 as shown in FIG. 4 (b) To do.

The circularly polarized light a ₄ emitted to the observation side of the liquid crystal element ₁ is substantially the same as the linearly polarized light a ₁ that is transmitted through the observation side polarizing plate 14 from the observation side and incident by the observation side λ / 4 plate 16. the same is linearly polarized light a ₅ incident on the observation side polarizing plate 14, the observation-side polarizer 14 transmitted is emitted to the observation side, the OFF voltage appears the color filter 6R for pixel a of applying, A bright display of any one of red, green, and blue colored by 6G and 6B is provided.

  In this reflective display, light that has entered the transmissive display portion A2 of the plurality of pixels A and transmitted through the liquid crystal layer 12 out of light incident from the observation side is on the opposite side of the liquid crystal element 1. Exit.

  That is, this liquid crystal display element performs a normally black mode reflective display in which the display when the OFF voltage is applied is a dark display. When aligned in the alignment state, the darkest dark display is black, and when the liquid crystal molecules 12a are in a tilted orientation by applying an ON voltage, the brightest bright display (colored by the color filters 6R, 6G, 6B) Red, green, and blue).

  Further, this liquid crystal display element is provided with reflecting means 8 for dividing the plurality of pixels A into a reflective display portion A1 and a transmissive display portion A2 on the substrate 3 opposite to the viewing side of the liquid crystal element 1, respectively. Therefore, the light absorption by the polarizing plate in the reflective display using the external light is only the absorption by the polarizing plate 14 on the observation side, and therefore the color image by the reflective display can be sufficiently brightened.

  In addition, in this liquid crystal display element, the color filters 6R, 6G, and 6B are each provided with an opening that partially corresponds to the reflective display portion A1 of the pixel A. Therefore, in the reflective display, a plurality of pixels are provided. The red, green, and blue colored light colored by the color filters 6R, 6G, and 6B and the openings of the color filters 6R, 6G, and 6B are transmitted from the reflective display portion A1 of A, respectively. The non-colored light can be emitted, and therefore the brightness of the reflective display is raised by the non-colored light, and a brighter color image can be displayed.

  Next, transmissive display using illumination light from the surface light source 19 will be described. FIG. 5 is a schematic diagram of transmissive display of the liquid crystal display element, and a transmissive display portion A2 of one pixel A of the liquid crystal element 1. Is shown.

  5A shows a display when an OFF voltage for aligning the liquid crystal molecules 12a in the initial vertical alignment state is applied between the electrodes 4 and 5 of the pixel A, and FIG. 5B shows an electrode of the pixel A. 4 shows a display when an ON voltage is applied between 4 and 5 to cause the liquid crystal molecules 12a to be in a tilted orientation.

In the liquid crystal display element, in the case of transmissive display using illumination light from the surface light source 19, the opposite side polarizing plate 15 disposed on the opposite side of the liquid crystal element 1 is used as a polarizer, and the liquid crystal display element is placed on the observation side of the liquid crystal element 1. The arranged observation-side polarizing plate 14 is displayed as an analyzer. In this transmissive display, as shown by arrows in FIGS. 5 (a) and 5 (b), from the opposite side to the observation side. The incident illumination light b ₀ is converted into linearly polarized light b ₁ parallel to the transmission axis 15 a by the opposite side polarizing plate 15, and further left or right as seen from the traveling direction of the light by the opposite side λ / 4 plate 17. The circularly polarized light b ₂ is incident on the liquid crystal layer 12 of the liquid crystal element 1.

  In this transmissive display, light incident on the liquid crystal element 1 among the light incident on the liquid crystal element 1 is incident on the liquid crystal layer 4 and incident on the reflective display portion A1. The light is reflected to the opposite side by the reflective film 8a.

When the OFF voltage is applied, the liquid crystal molecules 12a of the liquid crystal layer 12 are substantially vertically aligned, so that the opposite side λ / 4 plate 17 makes the circularly polarized light b ₂ and the transmissive display of the pixel A. the light incident on the part A2 emits the liquid crystal layer 12 on the observation side of the liquid crystal element 1 as shown in FIG. 5 and transmitted as the circularly polarized light b ₂ without being little birefringence effect (a).

The circularly polarized light b ₂ emitted to the observation side of the liquid crystal element 1 is substantially the same linearly polarized light as the linearly polarized light b ₁ transmitted through the opposite side polarizing plate 15 and incident by the observation side λ / 4 plate 16. is the b ₃ incident on the observation side polarizing plate 14 is absorbed by the observation side polarizing plate 14, the display of the pixel a was applied to the OFF voltage becomes dark display black.

In addition, when the ON voltage is applied, the liquid crystal molecules 12a of the liquid crystal layer 12 are aligned with the major axis in the direction along the rubbing directions 2a and 3a of the substrates 2 and 3 as described above. The light that has been made circularly polarized light b ₂ by the side λ / 4 plate 17 and incident on the transmissive display portion A 2 of the pixel A changes its polarization state due to the birefringence of the liquid crystal layer 12, and enters the observation side of the liquid crystal element 1. Exit.

The birefringence action of the liquid crystal layer 12 of the reflective display portion A1 when the ON voltage is applied is that Δnd2 of the transmissive display portion A2 when the liquid crystal molecules 12a are oriented in a tilted manner is 270 ± 40 nm as described above. Therefore, the light that has been made into the circularly polarized light b ₂ by the opposite side λ / 4 plate 17 and incident on the liquid crystal layer 12 of the transmissive display portion A 2 is transmitted by the liquid crystal layer 12. The circularly polarized light b ₄ is rotated in the reverse direction and emitted to the viewing side of the liquid crystal element 1 as shown in FIG.

The circularly polarized light b ₄ emitted to the viewing side of the liquid crystal element 1 is a straight line that is substantially orthogonal to the linearly polarized light b ₁ that has been transmitted through the opposite polarizing plate 15 and incident by the viewing side λ / 4 plate 16. is a polarization b ₅ incident on the viewing side polarizing plate 14, the observation-side polarizing plate 14 passes through to the exit to the observation side, see the color filter 6R for pixel a of applying the OFF voltage, 6G, 6B A bright display of one of red, green, and blue colors is obtained.

  That is, this liquid crystal display element performs normally black mode display even in transmissive display using the illumination light from the surface light source 19, and the display initially displays the liquid crystal molecules 12a by applying an OFF voltage. When the liquid crystal molecules 12a are tilted by applying an ON voltage, the brightest bright display (by the color filters 6R, 6G, and 6B) is obtained. Colored red, green and blue).

  In this transmissive display, the opposite-side polarizing plate 15 and the observation-side polarizing plate 14 are interposed in the path of light emitted from the surface light source 19 and emitted to the observation side of the liquid crystal display element. Since the light emitted from 19 only passes through each of the opposite side polarizing plate 15 and the observation side polarizing plate 14 once, the absorption of the light by the polarizing plate is the same as that in the reflection display. A bright display can be obtained.

  Therefore, according to this liquid crystal display element, it is possible to obtain a display with a wide viewing angle and a high contrast, and are arranged on the side opposite to the observation side and the color image display by reflection display using external light. Both the color image display by the transmissive display using the illumination light from the surface light source 19 can be performed, and both the color images can be brightened sufficiently.

  The surface light source 19 can also be used as an auxiliary light source in reflective display using external light. In this case as well, both the reflective display and the transmissive display are in a normally black mode. Can be obtained.

  Further, in this liquid crystal display element, since the liquid crystal layer thickness d1 of the reflective display portion A1 of the plurality of pixels A is smaller than the liquid crystal layer thickness d2 of the transmissive display portion A2, the liquid crystal layer of the reflective display portion A1. Reducing the difference between the birefringence action of the liquid crystal layer 12 with respect to the light transmitted back and forth through 12 and the birefringence action of the liquid crystal layer 12 with respect to the light transmitted through the liquid crystal layer 12 of the transmissive display portion A2 only once; Both the color image by the reflective display and the color image by the transmissive display can be displayed with almost no difference in quality.

  In this embodiment, the liquid crystal layer thickness d1 of the reflective display portion A1 is set to approximately ½ of the liquid crystal layer thickness d2 of the transmissive display portion A2, and when the ON voltage is applied (the liquid crystal molecules 12a have their molecular long axes in the rubbing direction. Since Δnd1 of the reflective display portion A1 and Δnd2 of the transmissive display portion A2 are set to Δnd1 = 140 ± 40 nm and Δnd2 = 270 ± 40 nm, respectively (when aligned and in a tilted orientation), as described above, In both the reflective display and the transmissive display, the darkest black dark display can be obtained by applying the OFF voltage, and the brightest bright display can be obtained by applying the ON voltage.

  In this embodiment, one of the pair of substrates 2 and 3 of the liquid crystal element 1, for example, the inner surface of the observation-side substrate 2 is associated with the reflective display portion A 1 of the plurality of pixels A to correspond to the reflective display portion A 1. Since the transparent film 9 for making the substrate gap smaller than the substrate gap of the transmissive display portion A2 of the pixel A is provided, the liquid crystal layer thickness d1 of the reflective display portion A1 of the plurality of pixels A can be set with a simple structure. It can be made smaller than the liquid crystal layer thickness d2 of the transmissive display portion A2.

  In the liquid crystal display element, the vertical alignment films 10 and 11 are formed on the inner surfaces of the pair of substrates 2 and 3 of the liquid crystal element 1, respectively, and the inner surfaces (film surfaces of the vertical alignment films 10 and 11) are mutually connected. Since the rubbing process is performed in the parallel direction, the tilting direction of the liquid crystal molecules 12a when the ON voltage is applied is defined as the direction along the rubbing directions 2a and 3a, and higher contrast can be obtained.

  Further, since this liquid crystal display element is provided with the diffusion layer 18 between the liquid crystal element 1 and the observation side λ / 4 plate 16, the reflected light from the reflection film 8a is transmitted to the diffusion layer 18 during the reflective display. The reflected display is further brightened and the viewing angle of both the reflective display and the transmissive display can be made wider.

  In the above embodiment, the inner surfaces (film surfaces of the vertical alignment films 10 and 11) of the pair of substrates 2 and 3 of the liquid crystal element 1 are rubbed in parallel and in opposite directions. The inner surfaces of the second and third surfaces may be rubbed in parallel and in the same direction, and in this case as well, in the same manner as in the above embodiment, the collapse direction of the liquid crystal molecules 12a when the ON voltage is applied is along the rubbing direction. Therefore, a higher contrast can be obtained.

  The rubbing treatment may be performed only on the inner surface of one of the pair of substrates 2 and 3 or may not be performed on either of the pair of substrates 2 and 3.

  FIG. 6 shows the second embodiment of the present invention when one of the pair of substrates 2 and 3, for example, only the inner surface of the opposite substrate 3 is subjected to a rubbing process, when an OFF voltage is applied to the liquid crystal molecules 12a. FIG. 6 is a schematic diagram showing an alignment state when an ON voltage is applied, and when the rubbing process is performed only on the inner surface of the opposite substrate 3 as in this embodiment, the liquid crystal molecules 12a are turned off by the OFF voltage shown in FIG. From the vertical alignment state at the time of application, by applying an ON voltage, as shown in FIG. 6 (b), the molecular major axis is aligned in the direction along the rubbing direction 3a of the opposite substrate 3 and collapsed substantially horizontally. In addition, the viewing angle of the display can be further widened because it is oriented in two directions opposite to each other with respect to the inner surface of the observation-side substrate 2 that is not subjected to the rubbing treatment.

  FIG. 7 is a schematic diagram showing the alignment state when the OFF voltage is applied to the liquid crystal molecules 12a and when the ON voltage is applied when the rubbing treatment is not performed on any of the pair of substrates 2 and 3 according to the third embodiment of the present invention. In the case where the rubbing treatment is not performed on any of the pair of substrates 2 and 3 as in this embodiment, the liquid crystal molecules 12a are from the vertical alignment state when the OFF voltage is applied as shown in FIG. By applying the ON voltage, as shown in FIG. 7 (b), the orientation is inclined in two directions opposite to each other with respect to the inner surfaces of the pair of substrates 2 and 3, so that the viewing angle of the display Can be made even wider.

  In the above embodiment, the reflecting means 8 for dividing the plurality of pixels A of the liquid crystal element 1 into the reflective display portion A1 and the transmissive display portion A2 respectively corresponds to the reflective display portion A1 for each of the plurality of pixels A. However, the diffusing layer 18 may be omitted by forming irregularities on the reflecting surface of the reflecting film that forms the reflecting means 8.

  FIG. 8 is a cross-sectional view of a part of a liquid crystal display device according to a fourth embodiment of the present invention. This liquid crystal display device has a liquid crystal element 1a in which reflecting means 8 is formed by a reflective film 8b having irregularities formed on the reflecting surface. It is equipped with.

  In this embodiment, the liquid crystal element 1 a is provided with a plurality of pixel electrodes 5, TFTs 7, gate wiring and data wiring (not shown) on the inner surface of the observation side substrate 2, and the reflecting means on the inner surface of the opposite side substrate 3. 8, an active matrix liquid crystal element provided with three color filters 6R, 6G, and 6B of red, green, and blue, a substrate gap adjusting transparent film 9, and a counter electrode 4, and forming the reflecting means 8 The reflective film 8b is deposited on the transparent uneven surface film 13 provided on the substrate surface of the opposite substrate 3 and having the entire surface formed as an uneven surface.

  In the liquid crystal display element of this embodiment, the structure of the liquid crystal element 1a is different from the liquid crystal element 1 of the first embodiment described above, and the diffusion layer 18 in the liquid crystal display element of the first embodiment is omitted. However, the values of Δnd1 of the reflective display portion A1 and Δnd2 of the transmissive display portion A2 of the liquid crystal layer 12 and the plurality of pixels A of the liquid crystal element 1a are the same as those of the first embodiment, and the polarizing plates 14 and 15 Since the arrangement state of the λ / 4 plates 16 and 17 is the same as that of the first embodiment, a duplicate description is omitted.

  In the liquid crystal display element of this embodiment, the reflective means 8 for dividing the plurality of pixels A of the liquid crystal element 1a into the reflective display part A1 and the transmissive display part A2, respectively, is provided for each of the plurality of pixels A. Therefore, the reflective display using external light can be brightened and the viewing angle can be further widened.

  Further, in this embodiment, since the uneven surface film 13 having the entire surface formed as an uneven surface is provided on the substrate surface of the opposite substrate 3 of the liquid crystal element 1a, and the reflective film 8b is formed thereon, the surface light source Also in the transmissive display using illumination light from 19, the light diffused by the uneven surface film 13 can be emitted and the viewing angle can be widened.

  In this embodiment, the reflective film 8b is deposited on the uneven surface film 13 to form the uneven surface on the reflective surface of the reflective film 8b. However, the uneven surface is formed on the reflective surface of the reflective film 8b. Other means may be used, and non-diffused light may be emitted during the transmissive display.

  In the liquid crystal display elements of the above-described embodiments, λ / 4 plates 16 and 17 are disposed between the pair of substrates 2 and 3 of the liquid crystal display elements 1 and 1a and the pair of polarizing plates 14 and 15, respectively. However, only one λ / 4 plate is disposed between the observation side substrate 2 and the observation side polarizing plate 14 between the pair of substrates 2 and 3 and the pair of polarizing plates 14 and 15. May be.

  In addition, the liquid crystal display element of each of the above embodiments includes the active matrix liquid crystal elements 1 and 1a, but the liquid crystal element may be a simple matrix type liquid crystal element.

1 is a cross-sectional view of a part of a liquid crystal display device showing a first embodiment of the present invention. The figure which shows the rubbing direction of a pair of board | substrate of the said liquid crystal display element, the direction of the transmission axis of the polarizing plate of an observation side and an other side, and the direction of the slow axis of (lambda) / 4 board of an observation side and an other side. The schematic diagram of the orientation state at the time of the OFF voltage application of the liquid crystal molecule in a 1st Example, and an ON voltage application. The schematic diagram of the reflective display of the said liquid crystal display element. The schematic diagram of the transmissive display of the said liquid crystal display element. The schematic diagram of the orientation state at the time of the OFF voltage application of the liquid crystal molecule and the ON voltage application which shows the 2nd Example of this invention. The schematic diagram of the alignment state at the time of OFF voltage application of the liquid crystal molecule and ON voltage application which shows the 3rd Example of this invention. Sectional drawing of the part of liquid crystal display element which shows 4th Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,1a ... Liquid crystal element, 2,3 ... Board | substrate, 4,5 ... Electrode, 6R, 6G, 6B ... Color filter, 7 ... TFT, 8 ... Reflection means, 8a, 8b ... Reflection film, A ... Pixel, A1 ... Reflective display part, A2 ... transparent display part, 9 ... transparent film for adjusting the substrate gap, 10,11 ... vertical alignment film, 2a, 3a ... rubbing direction, 12 ... liquid crystal layer, 12a ... liquid crystal molecule, 13 ... concave surface film, 14 , 15 ... polarizing plate, 14a, 15a ... transmission axis, 16, 17 ... λ / 4 plate, 16a, 17a ... slow axis, 18 ... diffusion layer, 19 ... surface light source.

Claims (4)

A pair of substrates on the opposite side and the observation side facing each other;
An electrode that is provided on each of the opposing inner surfaces of the pair of substrates and that forms a plurality of pixels by regions facing each other;
A color filter of three colors of red, green, and blue provided on one inner surface of the pair of substrates in correspondence with the plurality of pixels,
A reflective display unit that is provided on the opposite substrate and reflects light incident on the plurality of pixels from the observation side to the observation side, and a transmissive display unit that transmits light incident on the opposite side to the observation side. Reflecting means to be divided into
Liquid crystal molecules are sealed between the pair of substrates so as to be oriented substantially perpendicular to the substrate surface, and the layer thickness of the reflective display portion of the plurality of pixels is smaller than the layer thickness of the transmissive display portion. A liquid crystal layer made of a liquid crystal material having a negative dielectric anisotropy;
A pair of polarizing plates on the observation side and the opposite side disposed to face the outer surfaces of the pair of substrates, and
Of the pair of substrates and the pair of polarizing plates, at least one λ / 4 plate disposed between the substrate on the observation side and the polarizing plate,
A liquid crystal display element comprising:   A transparent film is provided on the inner surface of one of the pair of substrates so as to correspond to the reflective display portion of the plurality of pixels so that the substrate gap of the reflective display portion is smaller than the substrate gap of the transmissive display portion of the pixel. The liquid crystal display element according to claim 1.   2. The liquid crystal display element according to claim 1, wherein a vertical alignment film is formed on the inner surfaces of the pair of substrates, and the inner surfaces are rubbed in directions parallel to each other.   The reflecting means for dividing the plurality of pixels into the reflective display portion and the transmissive display portion each includes a plurality of reflective films provided corresponding to the reflective display portion for each of the plurality of pixels. The liquid crystal display element according to claim 1, wherein unevenness is formed on the reflection surface of the liquid crystal display element.

Images