JP2011186086A - Display panel or display device using display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a transmittance of an in-plane switching liquid crystal display panel is lower. <P>SOLUTION: The display panel includes: a pair of substrates; a medium which is disposed between the pair of substrates, exhibits optical isotropy when no voltage is applied, and exhibits optical anisotropy when a voltage is applied; a pixel electrode formed on one of the pair of substrates; a common electrode formed on the other; and a lighting unit for emitting light to the medium. The lighting unit makes the light impinge on the medium at a prescribed angle relative to a direction from the one substrate toward the other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a display panel or a display device using the display panel.

  Conventionally, a twisted nematic display system (hereinafter, “TN system”) liquid crystal display panel is known. Further, as a liquid crystal display element system for improving the contrast ratio (hereinafter referred to as “CR”) and viewing angle characteristics of the TN liquid crystal display element, for example, an in-plane switching (transverse electric field) display system (hereinafter referred to as “liquid crystal display device”). "IPS system") and multi-domain vertical alignment display system (hereinafter "VA system") are known.

  However, in the TN mode, IPS mode, or VA mode as described above, the nematic liquid crystal material used for the liquid crystal layer exhibits light scattering caused by molecular fluctuations. Since light is transmitted even in black display due to the light scattering, in a so-called normally black liquid crystal display panel that displays black when no voltage is applied, such as the IPS method and VA method, a reduction in CR is inevitable in principle. .

  Furthermore, since the change in orientation due to the self-orientation property of the liquid crystal layer is used, it is not possible to ensure sufficient speed response. Therefore, there is a problem that the image quality is deteriorated particularly in moving image display. Further, since the liquid crystal layer is an optically uniaxial medium, the transmittance depends on the viewing angle as it is.

  Therefore, in recent years, a liquid crystal display panel using a liquid crystal (hereinafter referred to as “isotropic liquid crystal”) material that is optically three-dimensional or two-dimensional isotropic has been proposed. In this isotropic liquid crystal, the alignment of liquid crystal molecules is optically isotropic in three dimensions or two dimensions when no voltage is applied to the liquid crystal layer, but when voltage is applied, birefringence is induced in the voltage application direction. Has properties.

  That is, such an isotropic liquid crystal induces optically uniaxial anisotropy in the voltage application direction only when a voltage is applied, and has no optical anisotropy when no voltage is applied. Therefore, light scattering that occurs when the above-described nematic liquid crystal material is used for black display does not occur.

  In addition, the isotropic liquid crystal utilizes an electro-optic effect, so that it can respond faster than a nematic liquid crystal material.

  The following materials have recently been reported as such isotropic liquid crystal materials. A smectic blue phase and a cholesteric blue phase have been reported as being three-dimensionally isotropic. In addition, bent type liquid crystal molecules, so-called bent core structures, have been reported as having two-dimensional isotropic properties. The bent core structure is obtained by vertically aligning a liquid crystal compound with respect to a substrate, and is isotropic in the plane of the liquid crystal layer when no voltage is applied. In addition, cubic phase, smectic Q phase, micelle phase, reverse micelle phase, sponge phase and the like are known.

  Regarding the isotropic liquid crystal, the following Non-Patent Document 1 discloses the expansion of the temperature range of the blue phase, which has been extremely narrow in the conventional temperature range and difficult to be applied to devices. Non-Patent Document 2 below discloses isotropic liquid crystal materials and properties such as optical biaxiality of the bent core structure. Further, Patent Document 1 below discloses a specific electrode structure of a liquid crystal panel using an isotropic liquid crystal.

JP 2006-3840 A

Harry J Coles, Nature, 436, 997-1000, 2005 Bharad R.D. Achayrya et al., LIQUID CRYSTALS TODAY, VOL. 13, no. 1, 1-4, 2004

  22A and 22B are diagrams for explaining the problem in the present invention. Specifically, FIG. 22A is a diagram schematically showing the arrangement of pixel electrodes and common electrodes viewed from the normal direction of the display screen in a liquid crystal display panel using isotropic liquid crystal, and FIG. It is a figure which shows roughly the cross section of the liquid crystal layer periphery in a panel.

  As shown in FIGS. 22A and 22B, the liquid crystal display panel 800 includes a pair of transparent substrates 805 and 806 and a liquid crystal layer 807 disposed between the pair of transparent substrates 805 and 806. Further, a comb-like pixel electrode 801 and a common electrode 802 are arranged on one substrate 805 of the pair of transparent substrates 805 and 806 to enable active matrix driving. On the other hand, a color filter 804 is disposed between the other substrate 806 and the liquid crystal layer 807. Note that an electrical wiring such as a thin film transistor (TFT) and an interlayer insulating film 803 are disposed over the substrate 805 where the pixel electrode and the like are disposed.

  Next, the operation of the liquid crystal display panel 800 will be described. When a voltage is applied to the pixel electrode 801 and the common electrode 802, an electric field component 813 is generated in the horizontal direction due to a potential difference between the electrodes. Therefore, in the liquid crystal layer 807, a refractive index change that is proportional to the first order of the electric field (Bockels effect) or proportional to the second order of the electric field (Kerr effect) occurs due to the electrooptic effect. As a result, birefringence in the horizontal plane appears in the liquid crystal layer 807, and bright display is possible by appropriately determining the orientation of the horizontal electric field.

  However, when a voltage is applied to the pixel electrode 801 and the common electrode 802 as described above, an electric field 814 in the substrate normal direction is mainly present in the liquid crystal layer 807 positioned immediately above the electrodes 801 and 802 as shown in FIG. 22B. Become. Therefore, when the liquid crystal layer 807 is an optically isotropic liquid crystal layer, the liquid crystal material immediately above the electrodes 801 and 802 hardly causes birefringence in the horizontal plane, and as a result, there is a problem that almost no light is transmitted. .

  Here, when the liquid crystal layer 807 is made of a nematic liquid crystal material instead of an isotropic liquid crystal material, the torsion due to the horizontal electric field between the electrodes propagates directly above the electrodes 801 and 802 immediately above because the continuum is strong. In addition, birefringence in the horizontal plane appears to some extent. Therefore, by using the electrodes 801 and 802 as transparent electrodes, light is transmitted to some extent directly above the electrodes.

  However, when an isotropic liquid crystal is used as described above, since the isotropic liquid crystal has a weak continuum property, almost no birefringence occurs in the horizontal plane immediately above the electrodes 801 and 802 and hardly transmits light. . As a result, light is transmitted only between the electrodes 801 and 802, and there is a problem that the transmittance of the liquid crystal layer 807 is lower than that in the case of using a nematic liquid crystal material.

  In order to suppress the above problems, it is conceivable to widen the electrode interval, but if this is done, the drive voltage increases. Although it is conceivable to reduce the electrode width, the drive voltage increases in the same manner, and the productivity is remarkably deteriorated.

  In view of the above problems, an object of the present invention is to provide a display panel using an isotropic medium having higher transmittance. The isotropic medium refers to a medium that generates optical anisotropy when a voltage is applied and optical anisotropy when a voltage is applied.

  (1) A display panel according to the present invention includes a pair of substrates, a medium that is disposed between the pair of substrates, generates optical isotropy when no voltage is applied, and generates optical anisotropy when a voltage is applied; A pixel electrode formed on one of a pair of substrates, a common electrode formed on the other, and an illumination unit that emits light to the medium, wherein the illumination unit transmits the light to the one The light is incident on the medium obliquely with respect to a direction from one substrate to the other substrate.

  (2) The display panel according to (1) further converts a direction of the light that has passed through the pair of substrates and the medium from the illumination unit to a direction from the one substrate toward the other substrate. It has the light direction conversion part which performs.

  (3) In the display panel according to (1), the light is light having maximum luminance among light emitted from the illumination unit.

  (4) In the display panel according to (1), each of the pair of substrates has a polarizing plate on a surface far from the medium.

  (5) In the display panel according to (1), the illumination unit has an angle of 40 degrees or more and less than 90 degrees in the air with respect to a direction in which the light is directed from the one substrate to the other substrate. It is made to inject with.

  (6) In the display panel according to (1), when the potential difference between the pixel electrode and the common electrode is 0, the medium has a substantially three-dimensional refractive index, and the pixel electrode When a potential difference is generated between the common electrodes, refractive index anisotropy is induced by an electro-optic effect.

  (7) In the display panel according to (1), the illumination unit includes at least one light source and a light guide plate that is arranged in line with the light source and guides light from the at least one light source. The surfaces of the light guide plate far from the pair of substrates are inclined at an angle of 1 ° or more with respect to a direction parallel to the pair of substrates.

で表わされる実効リタデーションＲ’が、前記光の波長５５０ｎｍに対して、２４０ｎｍ≦Ｒ’≦３１０ｎｍであることを特徴とする。 (8) In the display panel according to (1), an interval between the pixel electrode and the common electrode is d (nm), and an electric field in a direction from the one substrate applied to the medium to the other substrate is E. When the refractive index when E of the medium is 0 is n ₀ , the proportionality constant proportional to the refractive index of the medium is k, and the refractive index in the substrate normal direction of the medium is n ₀ + kE ² , Expressed in the medium

The effective retardation R ′ represented by the formula is characterized in that 240 nm ≦ R ′ ≦ 310 nm with respect to the wavelength of 550 nm of the light.

(9) In the display panel according to the above (1), when viewed from the direction from the one substrate to the other substrate, the smaller angle φ among the angles formed by the absorption axes of the respective polarizing plates. _P is 60 ° ≦ φ _P ≦ 88 °, and the light direction is characterized by forming an angle of φ _P / 2 with the absorption axis of each polarizing plate.

を満たすことを特徴とする。 (10) In the display panel according to (9), when the refractive index of the polarizing plate polarizing layer was n _P, the angle phi _P is

It is characterized by satisfying.

  (11) The display panel according to (1) further includes a birefringent film disposed between each polarizing plate and the medium, and the illumination unit transmits the light to the one of the ones. When viewed from the direction from the substrate to the other substrate, the light is emitted in all directions, the absorption axes of the polarizing plates are orthogonal to each other, the slow axes of the birefringent films are orthogonal to each other, The smaller angle formed by one of the absorption axes and the slow axis of each birefringent film is 45 °, and the retardation of each birefringent film is 100 nm or more and 150 nm with respect to the light having a wavelength of 550 nm. It is characterized by the following.

  (12) In the display panel according to (11), each of the birefringent films has an Nz coefficient of 0.4 or more and 0.6 or less.

  (13) In the display panel according to (11), the display panel further includes an optical phase compensation film between one of the polarizing plates adjacent to each other and one of the birefringent films. The optical phase compensation film has an Nz coefficient of 0.4 or more and 0.6 or less, a retardation of 240 nm or more and 300 nm or less with respect to the light having a wavelength of 550 nm, and the one substrate to the other substrate. One of the absorption axes of the respective polarizing plates and the slow axis of the optical phase compensation film are parallel or orthogonal to each other when viewed from the direction of the light.

  (14) In the display panel according to (1), the light beam direction conversion unit is a prism sheet.

  (15) In the display panel according to (1), the light beam direction conversion unit includes a prism sheet and a scattering sheet that scatters light emitted from the prism sheet.

  (16) In the display panel according to (15), the scattering sheet has a plurality of particles scattered inside, and when an average diameter of the scattering particles is L (nm), 0.4 < It is characterized by πL / 550 <3.

  (17) In the display panel according to (4), each of the polarizing plates has an antireflection film on a surface far from the medium.

を満たすことを特徴とする。 (18) In the display panel according to (17), when the refractive index of the antireflection film with respect to light having a wavelength of 550 nm is n _R and the film thickness is d _R nm, 1 ≦ n _R <1.5. And

It is characterized by satisfying.

  (19) In the display panel according to (11), the illumination unit includes a plurality of point light sources and light from each of the point light sources in a direction from the one substrate to the other substrate. It has the lens which makes the said predetermined angle and injects into the said medium, and has a diffusion part which diffuses the light from the said lens.

  (20) In the display panel described in (1) above, the medium is a liquid crystal that exhibits optical isotropy when no voltage is applied and optical anisotropy when a voltage is applied.

  An object of the present invention is to provide a display panel using an isotropic medium having higher transmittance. The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  A display panel using an isotropic medium with higher transmittance can be provided. Here, the isotropic medium refers to a medium that generates optical anisotropy when a voltage is applied as described above and also has optical anisotropy when a voltage is applied.

It is a figure for demonstrating the liquid crystal display panel in embodiment of this invention. It is the schematic which expanded one pixel of the liquid crystal display part in FIG. It is a figure which shows the result of having calculated the angle dependence of the effective retardation in embodiment of this invention. It is a figure for demonstrating the axial arrangement | positioning of the polarizing plate in embodiment of this invention. It is a figure for demonstrating the axial arrangement | positioning of the polarizing plate in embodiment of this invention. It is a figure for demonstrating the axial arrangement | positioning of the polarizing plate in embodiment of this invention. It is a figure for demonstrating the axial arrangement | positioning of the polarizing plate in embodiment of this invention. It is a figure which shows the relationship between the absorption-axis crossing angle in the embodiment of this invention, an effective absorption-axis crossing angle, and an output angle. It is a figure which shows the relationship between the absorption axis crossing angle in the embodiment of this invention, an output angle, and the transmittance | permeability. It is a figure for demonstrating the illumination part in embodiment of this invention. It is a figure which shows the relationship between the outgoing angle and the transmittance | permeability at the time of the bright display and dark display in this Embodiment. It is a figure for demonstrating the light direction conversion part in this Embodiment. It is a figure which shows the light direction conversion part in the modification 1. It is a figure for demonstrating the structure of the illumination part in the modification 2. FIG. It is a figure for demonstrating the illumination part in the modification 3. FIG. It is a figure for demonstrating the liquid crystal display panel in the modification 4. It is a figure which shows the result of having calculated | required the relationship between the emission angle of the emitted light from an illumination part, and the transmittance | permeability about each at the time of the bright display in the modification 4, and a dark display. It is a figure for demonstrating the structure of the illumination part in the modification 5. FIG. It is a figure for demonstrating the structure of the liquid crystal display part in the modification 5. FIG. It is a figure for demonstrating axial arrangement | positioning, such as a polarizing plate in the modification 5. FIG. It is a figure which shows the result of having calculated | required the transmittance | permeability about each at the time of the bright display in the modification 5, and a dark display. It is a figure for demonstrating the subject of this invention. It is a figure for demonstrating the subject of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, about drawing, the same code | symbol is attached | subjected to the same or equivalent element, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a diagram for explaining a liquid crystal display panel according to an embodiment of the present invention. As shown in FIG. 1, the liquid crystal display panel 100 includes an illumination unit 111, a liquid crystal display unit 110, and a light direction conversion unit 112.

  The liquid crystal display unit 110 includes a first substrate 105 and a second substrate 106 which are disposed to face each other, and an optically isotropic liquid crystal layer (hereinafter referred to as an “isotropic liquid crystal layer”) is interposed between the first substrate 105 and the second substrate 106. “Liquid crystal layer”) 107 is arranged.

  The first substrate 105 includes the pixel electrode 101 on the surface closer to the liquid crystal layer 107 and the first polarizing plate 108 on the surface farther from the liquid crystal layer 107. The second substrate 106 includes the common electrode 102 on the surface closer to the liquid crystal layer 107 and the second polarizing plate 109 on the surface farther from the liquid crystal layer 107. Specifically, the pixel electrode 101 and the common electrode 102 are formed to face each other so as to cover the surfaces of the first substrate and the second substrates 105 and 106, respectively.

  With this arrangement, an electric field in the normal direction 115 (substrate normal direction) of the first and second substrates 105 and 106 is applied to the liquid crystal layer 107 due to a potential difference between the pixel electrode 101 and the common electrode 102. It can be applied uniformly at 107.

  In addition, an illumination unit 111 is disposed on the back surface of the liquid crystal display unit 110, and a light direction conversion unit 112 is disposed on the front surface. In FIG. 1, the lower side corresponds to the back surface, and the upper side corresponds to the front surface.

  The illumination unit 111 is a so-called backlight that emits light to the liquid crystal display unit 110. Specifically, the illumination unit 111 emits light obliquely in a direction inclined by an angle θ in the air mainly with respect to the substrate normal direction 115 of the first and second substrates 105 and 106. The specific configuration of the illumination unit 111 will be described later. The light inclined by the angle θ means that the light distribution from the illumination unit 111 is centered on the θ. In other words, the light having the maximum luminance in the light distribution is located at the angle θ.

  FIG. 2 is an enlarged schematic view of one pixel of the liquid crystal display unit 110 in FIG. Although omitted in FIG. 1 for simplification of the drawing, as shown in FIG. 2, an electrical wiring such as a thin film transistor (TFT) capable of active matrix driving, between the first substrate 105 and the pixel electrode 101, An interlayer insulating film 103 or the like is disposed. In addition, a color filter 104 is disposed between the second substrate 106 and the common electrode 102.

  The configuration of the liquid crystal display panel is an example, and it can be replaced with a configuration that is substantially the same as the configuration described above, a configuration that exhibits the same operational effects, or a configuration that can achieve the same purpose. Not too long.

  Next, the operation of the liquid crystal display panel 100 in the present embodiment will be described. As described above, the emitted light 113 from the illumination unit 111 is incident on the liquid crystal layer 107 with an angle θin with respect to the substrate normal direction 115.

  At the time of bright display, a potential difference is applied between the pixel electrode 101 and the common electrode 102 which are arranged to face each other. As a result, an electric field 116 is generated in the substrate normal direction 115 in the liquid crystal layer 107, and uniaxial anisotropic birefringence with the maximum refractive index in the substrate normal direction 115 appears.

  Here, as in the liquid crystal display panel 800 illustrated in FIG. 22B, when the emitted light from the illumination unit 111 is mainly in the substrate normal direction 115, the emitted light is affected by the birefringence of the liquid crystal layer 107. There is little to receive. However, as shown in FIG. 2, when the outgoing light 113 is incident on the liquid crystal layer 107 obliquely, that is, with a predetermined angle, for example, θ, with respect to the substrate normal direction 115, birefringence to be influenced.

  Therefore, the polarization state of light transmitted through the liquid crystal layer 107 can be changed when a voltage is applied. That is, bright display and dark display on the liquid crystal display panel 100 can be controlled by the presence or absence of voltage application to the liquid crystal layer 107.

  The outgoing light 113 transmitted through the liquid crystal layer 107 controlled as described above is then transmitted through the second polarizing plate 109. Thereafter, the light direction conversion unit 112 converts the traveling direction of the emitted light 113 to be mainly parallel to the substrate normal direction 115.

  With the configuration described above, according to the present embodiment, the electric field 116 can be uniformly generated in the substrate normal direction 115 between the pixel electrode 101 and the common electrode 102 during bright display. Therefore, birefringence can be generated in the light that is uniformly transmitted through the liquid crystal layer 107 as compared with the case where the comb-shaped electrodes 801 and 802 shown in FIG. 22 are used. Therefore, even when an isotropic liquid crystal is used for the liquid crystal layer 107, the liquid crystal display panel 100 having a very high transmittance equivalent to that of the TN mode can be obtained.

  Further, according to the present embodiment, the driving voltage of the liquid crystal display unit 110 can be lowered as the distance between the pixel electrode 101 and the common electrode 102, the so-called cell gap, is reduced. Specifically, it will be described below.

When the cell gap is d and the potential difference between the pixel electrode 101 and the common electrode 102, that is, the drive voltage is V, the electric field E generated in the liquid crystal layer 107 is expressed by the following equation.
E = V / d (1)

The change nz of the refractive index in the substrate normal direction 115 in the liquid crystal layer 107 due to the Kerr effect is expressed by the following equation, where n ₀ is the refractive index of the liquid crystal layer 107 when no electric field is applied.
nz = n ₀ + kE ² (2)

Here, k is a proportional coefficient and depends on the liquid crystal material.
Next, it is assumed that the refractive index in air is 1, the average refractive index of the liquid crystal layer 107 is (n _e + n ₀ ) / 2, and ordinary light and extraordinary light have the same optical path. As shown in FIGS. 1 and 2, the following equation is established from Snell's law when the emission angle θ of light emitted from the illuminating unit 111 in the air and the light traveling direction in the liquid crystal layer 107 are θ _in .

次に、上記式（３）を考慮して、屈折率楕円体の議論から照明部１１１からの出射光に影響する複屈折を求める。実効的常光屈折率と異常光屈折率の差をΔｎ’とすれば、これはｎｚ及びθの関数として、次式で表わされる。

Next, in consideration of the above formula (3), birefringence that affects the light emitted from the illumination unit 111 is obtained from the discussion of the refractive index ellipsoid. If the difference between the effective ordinary refractive index and the extraordinary refractive index is Δn ′, this is expressed by the following equation as a function of nz and θ.

  By applying the above equation (2) to this, the following equation is obtained.

In addition, since the distance that light travels in the liquid crystal layer 107 is d / cos θ _in , considering the above equation (3), the effective retardation R ′ of the liquid crystal layer 107 with respect to the light emitted from the illumination unit 111 is expressed by the following equation: Represented.

  If the above equation (1) is applied to this equation, the effective retardation R ′ can be obtained as a function of V, d, and θ.

  As will be described later, V, d, and θ may be set so as to satisfy this effective retardation R′≈λ / 2 with respect to light of wavelength λ. Specifically, if general wavelength dispersion is assumed for each optical member, it is desirable that 240 nm ≦ R ′ <310 nm with respect to the wavelength of 550 nm. Alternatively, when the liquid crystal display unit 110 includes the color filter 104, the cell gap d or the driving voltage V may be adjusted for each color.

  From the above, it can be seen that the effective retardation R ′ becomes larger as the cell gap d is smaller, except in the extreme case where the cell gap d is 0.1 μm.

FIG. 3 is a diagram showing the results of calculating the angular dependence of the effective retardation R ′ when k = 0.02, V = 10 V, and n ₀ = 1.5. In FIG. 3, the vertical axis represents effective retardation (nm), and the horizontal axis represents the emission angle (°) of light from the illumination unit 111 in the air.

  As can be seen from FIG. 3, R ′ increases as the cell gap decreases. It can also be seen that R ′ can be increased as the outgoing light angle θ from the illumination unit 111 is increased.

  However, when θ is increased as will be described later, the interface reflection increases and as a result, the transmittance decreases. Therefore, 40 ° ≦ θ <90 ° is desirable.

  Here, the property that R 'increases when d is reduced is significantly different from the liquid crystal display panel to which optically isotropic liquid crystal is applied in the prior art. In the conventional liquid crystal display panel, as can be seen from FIG. 22, for example, in order to increase the effective retardation, it is necessary to increase the horizontal electric field component 813 or increase the cell gap. As for the former, as described above, there is a problem that the transmittance during bright display is lowered. As for the latter, the effect can be expected up to the cell gap of the same degree as the electrode width and the electrode interval. This is because the horizontal electric field component 813 decreases as the distance from the electrode increases in the substrate thickness direction. Therefore, it eventually leads to a problem of a decrease in transmittance. Further, since the volume of the liquid crystal layer 107 is increased, there is a problem that the material cost is increased. According to the liquid crystal display panel 100 according to the present embodiment, such a problem can be solved at the same time.

  The above is the basic configuration and operation of the liquid crystal display panel 100 in the present embodiment. Hereinafter, the axial arrangement of the polarizing plates 108 and 109 and the specific configuration of the illumination unit 111 will be described in detail.

  First, the axial arrangement of the first polarizing plate 108 and the second polarizing plate 109 for obtaining good bright display and dark display will be described. FIG. 4 shows a state in which the absorption axis of the first polarizing plate, the absorption axis of the second polarizing plate, and the azimuth relationship of the emitted light from the illumination unit are projected onto the front surface of the liquid crystal display unit.

In the conventional liquid crystal display panel, the angle φ _P formed by the polarizing plate absorption axes 417 and 418 is set to 0 ° or 90 °. However, in the liquid crystal display panel according to the present embodiment, as described above, the illumination unit Since the outgoing light 113 from 111 is incident on the liquid crystal layer 107 obliquely, φ _P <90 °.

In addition, an angle φ _B formed by the polarizing plate absorption axes 117 and 118 and the traveling direction 113 of the light emitted from the illumination unit 111 is φ _B = φ _P / 2. As a result, a good black display (dark display) when no voltage is applied to the liquid crystal layer 107 and a good white display (bright display) when a voltage is applied to the liquid crystal layer 107 can be obtained. Details will be described below.

First, the bright display will be described. This can be understood by using a Poincare sphere as shown in FIG. The polarization state P _T1 of the transmitted light of the first polarizing plate 108 and the polarization state P _T2 transmitted through the second polarizing plate 109 exist on the S ₁ -S ₂ plane of the Poincare sphere (S ₁ and S ₂ are Stokes parameters). In order to maximize the transmittance during bright display, it is necessary to cause a change in polarization state that converts P _T1 to P _T2 in the liquid crystal layer 107.

In FIG. 5, P _T1 and P _T2 are located at line target positions with the S ₁ axis as the axis of symmetry. Therefore, the retardation of the liquid crystal layer 107 needs to be λ / 2 with respect to incident light having a wavelength λ. Further, the slow axis of the liquid crystal layer 107 must be at the position of the S ₁ axis in the Poincare sphere. As described above with reference to FIG. 3, the former can be achieved by appropriately setting the drive voltage and the cell gap. The latter can be achieved by taking an axial arrangement (φ _B = φ _P / 2) as shown in FIG. That is, for example, when φ _P = 90 °, φ _B = 45 °, which is a well-known condition.

  Next, the dark display will be described. Here, a three-dimensional angle in the present embodiment is defined. As shown in FIG. 6, when xyz coordinates are applied to a plane 119 parallel to the substrates 105 and 106, the angle formed by the xy orthogonal projection 121 of the three-dimensional vector 120 and the x axis is the azimuth angle 122, and the vector 120 is the z axis. The angle formed is called the polar angle 123.

  During dark display, since no voltage is applied to the liquid crystal layer 107, the liquid crystal layer 107 is in an optically isotropic state. That is, only the polarizing plates 108 and 109 affect the dark display.

  In the liquid crystal display panel according to this embodiment, as described above, the emitted light 113 from the illumination unit 111 enters and exits the polarizing plates 108 and 109 obliquely. Therefore, in this case, the angle formed by the absorption axes 117 and 118 of the polarizing plates 108 and 109 depends on the incident angle. In order to obtain a good black display, the effective absorption axis crossing angle, that is, the absorption axis crossing angle viewed from the outgoing light 113 from the illumination unit 111 incident obliquely must be 90 °.

In order to explain the above, a coordinate system viewed from the substrate normal direction 115 in FIG. 7 is used. As shown in FIG. 7, it is assumed that the absorption axis 117 of the first polarizing plate 108 and the absorption axis 118 of the second polarizing plate 109 form an angle of φ _B0 with the x axis and the y axis, respectively. In order to maximize the transmittance during bright display, as described above, the emitted light 113 from the illumination unit 111 must be φ _B = φ _P / 2. Therefore, from FIG. 7, φ _P = 90 ° −2φ _B0 . That is, in order to maximize the transmittance at the time of bright display, the emitted light 113 from the illumination unit 111 travels in the direction of the azimuth angle φ _B0 + φ _P / 2 = 45 °, and enters and exits the polarizing plate. There is a need to.

As can be seen from the above, the effective absorption axis crossing angle φ _P ′ depends on the absorption axis crossing angle φ _P when viewed from the substrate normal direction 115 and the incident angle θ of the incident light of the polarizing plate in the air. According to our study, this correlation is expressed by the following equation. N _P represents the refractive index of the polarizing plate polarizing layer.

FIG. 8 shows the result of calculating φ _P ′ using this. In FIG. 8, the vertical axis represents the effective absorption axis crossing angle φ _P ′ (°), and the horizontal axis represents the absorption axis crossing angle φ _P (°) when viewed from the substrate normal direction 115. The refractive index n _P of the polarizing plate was calculated as a general value 1.5. From FIG. 8, the correlation of phi _P and phi _{P 'by} exit angle θ in air of the light emitted from the illumination unit 111 can be understood to vary.

Specifically, φ _P ′ becomes larger than φ _{P as} θ increases. From FIG. 8, when determining the approximate phi _P becomes _{φ P '= 90 °, θ} = 40 °, 60 °, relative in each case _{80 °, φ P = 85 °} , 78 °, is 75 ° . Therefore, in consideration of the width of the refractive index and the like, it is desirable that 60 ° ≦ φ _P ≦ 88 ° when a polarizing plate having a refractive index of about 1.5 is used.

If this optimum phi _P and phi _P0, phi _P0 is obtained by a φ _P '= 90 ° in the above equation (7), it is expressed by the following equation.

For the phi _P, according to our study, for _{example, φ P0 -2 ° ≦ φ P} ≦ φ P0 + 2 to a ° is desirable.

  FIG. Opt. Soc. Am. The title of the article “Optical in Stratified and Anisotropic Media: 4 × 4-Matrix Formulation”. W. BERREMAN, 1972, Volume 62, no. 4, PP. The results confirmed by optical simulation using the 44 matrix method disclosed in 502-510, are shown.

From FIG. 9, for example, when φ _P = 85 °, the transmittance is surely minimum in the vicinity of θ = 40 °, and the axial arrangement of the polarizing plates 108 and 109 may be set as described above. In FIG. 9, the vertical axis represents the transmittance (%), and the horizontal axis represents the emission angle θ (°) in the air of the emitted light from the illumination unit 111.

  Next, the illumination part 111 in this Embodiment is demonstrated. FIG. 10 is a diagram for explaining the configuration of the illumination unit 111. As shown in FIG. 10, the illumination unit 111 includes a fluorescent tube 125, a reflection plate 126, and a light guide plate 124 as viewed from the cross section.

  The reflection plate 126 reflects the emitted light from the fluorescent tube 125 and efficiently enters the emitted light into the light guide plate 124.

  The light guide plate 124 has an upper surface 901 and a lower surface 902 on a flat plate arranged to face each other. The light guide plate 124 is disposed closer to the upper surface 901 and farther from the liquid crystal display unit 110. Each of the upper surface 901 and the lower surface 902 is connected to the reflecting plate 126 at one end thereof. Further, the normal direction of the upper surface 901 is arranged to be substantially the same as the substrate normal direction 115 of the liquid crystal display unit 110 described above. The lower surface 902 is formed to be inclined with respect to the upper surface 901, that is, to have a predetermined angle.

With the above configuration, most of the light incident on the light guide plate 124 propagates through the light guide plate 124 while being totally reflected at the light guide plate 124 or the air interface, but the lower surface of the light guide plate 124 is inclined. As shown in FIG. 10, as light propagates, the reflection angle of the lower surface of the light guide plate 124 increases (θ ₂ > θ ₁ ), and the incident angle from the light guide plate 124 to the air interface decreases. In this way, the light exceeding the critical angle is sequentially emitted into the air.

  The emission angle θ into the air has a certain extent according to the emission distribution of the emitted light from the fluorescent tube 125, but the half-value angle is extremely small as compared with the case of the general illumination unit 111. Hereinafter, this central value is referred to as an emission angle θ.

  The tilt angle of the lower surface of the light guide plate 124 is determined by the display area of the liquid crystal display panel, but is preferably larger than 1 °. Further, the emission angle θ can be controlled by the refractive index of the light guide plate 124, the lower surface tilt angle, the lower surface reflection characteristics, the upper surface shape, or the optical member disposed between the light guide plate 124 and the liquid crystal display unit 110. In the above description, except for the configuration of the lower surface 902 of the light guide plate 124, the specific configurations of the reflector 126, the fluorescent tube 125, and the like are well known, and thus description thereof is omitted.

FIG. 11 shows the relationship between the outgoing angle θ of the outgoing light from the illumination unit 111 and the transmittance in the air during bright display and dark display in the present embodiment. 11, the polarizing plate absorption axis crossing angle φ _P = 78 ° when viewed from the substrate normal line, the polarizing plate refractive index of 1.5, and the optically isotropic liquid crystal layer 107 are shown in FIG. N ₀ = 1.5, k = 0.035, cell gap d = 3 μm, voltage V = 10 V between the pixel electrode 101 and the common electrode 102 at the time of bright display.

  As shown in FIG. 11, at θ = 60 °, the transmittance during bright display is high and the transmittance during dark display is low. At θ = 60 °, the transmittance during bright display is about 24%, and the transmittance ratio between bright display and dark display, so-called CR is 22000. That is, according to the present embodiment, both the transmittance and contrast ratio during bright display can be greatly improved as compared with the conventional liquid crystal display panel.

Next, the structure of the light direction conversion part in this Embodiment is demonstrated. As shown in FIG. 12, the light direction conversion unit 112 is formed by an inverted prism sheet 127 having a function of collecting obliquely incident light in the substrate normal direction 115. In addition, since the prism sheet itself is well-known, in this Embodiment, detailed description other than the description regarding prism apex angle (theta) _P is abbreviate | omitted.

In this embodiment, in order to convert the light having the incident angle θ into the substrate normal direction 115 as described above, when using a so-called positive prism having a light exit surface as a prism surface as shown in FIG. The angle θ _P may satisfy the following equation.

On the other hand, when using a so-called reverse prism to the light incident surface and the prism surface, the prism apex angle theta _P may satisfy the following equation.

In the present embodiment, for example, the inverted prism sheet 127 is used as the light direction conversion unit 112 and the prism apex angle θ _P is set to 71 °. However, the prism apex angle θ _P is calculated using the above formulas (9) and ( It suffices if it is within a range of about ± 5 ° from the central value determined in 10).

  By using the light direction conversion unit 112 as described above, the direction of light from the liquid crystal display unit 110 can be converted into the substrate normal direction 115. For example, when it is assumed that the liquid crystal display panel is viewed mainly from an oblique direction, such as a liquid crystal display device for car navigation, it is possible to view the liquid crystal display panel without providing a light beam direction portion. Is possible. In such a case, it goes without saying that the light direction changing unit 112 is not necessarily provided.

  As described above, according to the liquid crystal display panel in this embodiment, an electric field can be uniformly applied to the liquid crystal layer during bright display, and a liquid crystal display panel having a liquid crystal layer with high transmittance can be realized. it can. In addition, since the cell gap can be reduced, the liquid crystal layer can have a high transmittance and can be driven with a low driving voltage. In addition, the material cost of the liquid crystal layer can be reduced, and as a result, a highly productive liquid crystal display panel can be provided.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. That is, it can be replaced with a configuration that is substantially the same as the configuration described in the above embodiment, a configuration that exhibits the same operational effects, or a configuration that can achieve the same purpose.

  For example, in the above-described embodiment, the fluorescent tube 125 is used as the light source of the illumination unit 111. However, other light sources such as LEDs (Light Emitting Diodes) may be used as long as they are linear light sources arranged at the end of the light guide plate 124. But you can. Further, in the above embodiment, the illumination unit 111 as shown in FIG. 10 is used. However, as long as the light is incident obliquely on the liquid crystal layer 107 as described above, for example, different configurations as shown below are used. The illumination unit 111 may be used. Furthermore, as for the light direction conversion unit 112, as long as the direction of the emitted light 113 can be converted into the substrate normal direction 115, for example, a light direction conversion unit having a different configuration as shown below may be used.

[Modification 1]
The present modification is different from the above embodiment in that the light direction changing unit is formed of a prism sheet and a Mie scattering sheet. Other points are the same as those in the above embodiment, and the description of the same points is omitted.

  FIG. 13 is a diagram illustrating a light direction conversion unit in the present modification. As shown in FIG. 13, the light direction conversion unit 212 is formed of an inverse prism sheet 127 and a Mie scattering sheet 128.

  The outgoing light 113 from the liquid crystal display unit 110 is first converted in the traveling direction mainly into the substrate normal direction 115 by the inverted prism sheet 127 as in the above embodiment. Thereafter, as shown in FIG. 13, the Mie scattering sheet 128 travels in the substrate normal direction 115 while being scattered forward and is emitted into the air.

  Specifically, as shown in FIG. 13, scattering particles 301 having a diameter larger than the wavelength of light are dispersed in the Mie scattering sheet 128. According to the scattering theory, assuming that the average diameter of the scattering particles is L and the incident light wavelength is λ, if the particle size parameter α expressed by the following equation is 0.4 <α <3, the Mie scattering region is assumed. The light from the prism sheet can be scattered.

  As described above, by imparting scattering characteristics to the light direction conversion unit 212, it is possible to prevent the emitted light 113 from the liquid crystal display unit 110 from being condensed in the substrate normal direction 115 and to be seen from an oblique direction. Can do. Moreover, forward scattering can be made larger than backward scattering by using Mie scattering, and light loss can be minimized. In applications where light loss need not be considered, so-called Rayleigh scattering may be used.

  Further, as in the above embodiment, the liquid crystal display panel according to this modification can uniformly apply an electric field to the liquid crystal layer during bright display, and realizes a liquid crystal display panel having a liquid crystal layer with high transmittance. can do. In addition, since the cell gap can be reduced, the liquid crystal layer can have a high transmittance and can be driven with a low driving voltage. In addition, the material cost of the liquid crystal layer can be reduced, and as a result, a highly productive liquid crystal display panel can be provided.

  In addition, the structure of the said light direction conversion part is not limited above, A various deformation | transformation is possible. That is, it is needless to say that the configuration can be replaced with a configuration that is substantially the same as the configuration described above, a configuration that exhibits the same operational effects, or a configuration that can achieve the same purpose.

[Modification 2]
In this modification, the configuration of the lower surface of the illumination unit is different from that of the above embodiment. Other points are the same as those in the above embodiment, and the description of the same points is omitted.

  FIG. 14 is a diagram for explaining the configuration of the illumination unit in the present modification. As shown in FIG. 14, the lower surface 324 of the light guide plate 224 of the illumination unit 311 has grooves 129 at predetermined intervals. Specifically, a smooth recess is formed so that the lower surface 324 moves away from the liquid crystal display unit 110 as it goes to each groove 129.

  With the configuration described above, most of the light emitted from the fluorescent tube 125 and incident inside the light guide plate 224 propagates while being totally reflected inside the light guide plate 224. However, as shown in FIG. 14, the light incident on the groove 129 has a smaller reflection angle on the lower surface of the light guide plate 224, and enters the light guide plate 224 upper surface 325 and the air interface at an angle smaller than the critical angle. Thereby, the light is emitted mainly in the θ direction. Needless to say, the emission angle θ into the air can be controlled by the refractive index of the light guide plate 224, the shape of the groove 129, and the like.

  With the configuration as described above, the liquid crystal display panel according to this modification example can apply an electric field uniformly to the liquid crystal layer during bright display, and has a high transmittance as in the above embodiment. A liquid crystal display panel having the above can be realized. In addition, since the cell gap can be reduced, the liquid crystal layer can have a high transmittance and can be driven with a low driving voltage. In addition, the material cost of the liquid crystal layer can be reduced, and as a result, a highly productive liquid crystal display panel can be provided.

  In the present modification, the fluorescent tube 125 is used as the light source of the illumination unit 311. However, it may be a linear light source disposed at the end of the light guide plate 224, and may be an LED (Light Emitting Diode), for example.

  Moreover, the said illumination part is not limited to the above, A various deformation | transformation is possible. That is, it can be replaced with a configuration that is substantially the same as the configuration described above, a configuration that exhibits the same operational effects, or a configuration that can achieve the same purpose.

[Modification 3]
In this modification, the configuration of the illumination unit is different from that of the above embodiment. Other points are the same as those in the above embodiment, and the description of the same points is omitted.

  FIG. 15 is a diagram for explaining an illumination unit in the present modification. As shown in FIG. 15, the illumination unit 411 in this modification is formed by connecting two illumination units 111 in the above embodiment at the end opposite to the fluorescent tube 125. That is, the illumination unit 411 has a configuration that is bilaterally symmetric with respect to the center of the cross section.

Therefore, the outgoing angle of the outgoing light 113 from the illumination unit 411 is common to both outgoing lights of both fluorescent tubes 125 arranged on the left and right with respect to the polar angle θ. On the other hand, the azimuth angle differs by 180 ° for both outgoing lights from both fluorescent tubes 125. However, in FIG. 7, as can be seen by rotating the outgoing light 113 from the illumination unit 411 by 180 °, any outgoing light satisfies the condition of φ _B = φ _P / 2, and the effective absorption axis crossing angle φ _P ′. Is also common. Therefore, the light emitted from both fluorescent tubes 125 can have the same characteristics for both the dark display and the bright display of the liquid crystal display panel.

  With the configuration as described above, the liquid crystal display panel according to this modification example can apply an electric field uniformly to the liquid crystal layer during bright display, and has a high transmittance as in the above embodiment. A liquid crystal display panel having the above can be realized. In addition, since the cell gap can be reduced, the liquid crystal layer can have a high transmittance and can be driven with a low driving voltage. In addition, the material cost of the liquid crystal layer can be reduced, and as a result, a highly productive liquid crystal display panel can be provided.

  In this modification, the fluorescent tube 125 is used as the light source of the illuminating unit 411. However, it may be a linear light source disposed at the end of the light guide plate 124, and may be an LED (Light Emitting Diode), for example.

  In addition, the structure of the said light direction conversion part is not limited above, A various deformation | transformation is possible. That is, it can be replaced with a configuration that is substantially the same as the configuration described above, a configuration that exhibits the same operational effects, or a configuration that can achieve the same purpose.

[Modification 4]
FIG. 16 is a diagram for explaining a liquid crystal display panel according to this modification. This modification is different from the above embodiment in that the liquid crystal display unit has an antireflection film. Other points are the same as those in the above embodiment, and the description of the same points is omitted.

  Specifically, in this modification, as shown in FIG. 16, an antireflection film 139 is disposed on the surface of the first polarizing plate 108 that is far from the liquid crystal layer 107. Further, the antireflection film 140 is also disposed on the surface of the second polarizing plate 109 far from the liquid crystal layer 107, that is, the antireflection film 140 is disposed between the second polarizing plate 109 and the light direction conversion unit 112. Be placed.

In this modification, for example, as the polarizing plate 108 and 109, for example, when the refractive index of the polarizing plate and n _P, the refractive index along a thickness direction from the side closer to the polarizing plate and n _P to 1 The antireflection films 139 and 140 that change are used, but as the antireflection film, a low refractive index film or an antireflection film disclosed in Japanese Patent Application Laid-Open No. 2008-233850 may be used.

When a low refractive index film is used, when the refractive index is n _R and the film thickness is d _R (nm), importance is placed on reducing the reflectance with respect to light having an incident angle θ and a wavelength of 550 nm, and the following equation is satisfied. It is desirable.

  FIG. 17 is a diagram illustrating a result of obtaining the relationship between the emission angle θ of the emitted light from the illumination unit in air and the transmittance for each of bright display and dark display in this modification. As shown in FIG. 17, at θ = 60 °, the transmittance during bright display is about 29%. Therefore, a liquid crystal display panel with higher transmittance can be realized.

  Here, in the present modification, the antireflection film as described above is used from the following viewpoints. With the absorption axis of the pair of polarizing plates used in the above embodiment being parallel, the transmittance when light is incident on the front is about 32%. As described above, since the transmittance at the time of bright display obtained in the above embodiment is about 24%, it is considered that the light loss is large. As this factor, it is considered that the reflection between the polarizing plate and the air interface is the largest. When light in the substrate normal direction is mainly used as in a general liquid crystal display panel, this reflection loss is about 4% of the total, but a predetermined angle from the normal direction is set as in the above embodiment. In the case of mainly using light that has been emitted, according to the reflection coefficient of Fresnel, several percent of reflections occur depending on the angle. Therefore, according to this modification, it is possible to realize a liquid crystal display panel with higher transmittance by using the antireflection film as described above, reducing the light loss as described above.

  Further, according to the liquid crystal display panel in this modification, an electric field can be uniformly applied to the liquid crystal layer during bright display, and a liquid crystal display panel having a liquid crystal layer with high transmittance can be realized. The point is the same as that of the said embodiment. Similarly, since the cell gap can be reduced, a liquid crystal layer having a high transmittance can be provided and the liquid crystal layer can be driven with a low driving voltage. Furthermore, the material cost of the liquid crystal layer can be reduced, and as a result, a highly productive liquid crystal display panel can be provided.

  The configuration of the liquid crystal display unit is not limited to the above, and various modifications can be made. That is, it can be replaced with a configuration that is substantially the same as the configuration described above, a configuration that exhibits the same operational effects, or a configuration that can achieve the same purpose.

[Modification 5]
In the present modification, the configurations of the illumination unit and the liquid crystal display unit are mainly different from the above embodiment. In the following, description of the same points as in the above embodiment will be omitted.

  FIG. 18 is a diagram for explaining the configuration of the illumination unit in the present modification. As illustrated in FIG. 18, the illumination unit 511 includes point light sources 130, for example, LED light sources, arranged on the lower surface 512 of the illumination unit 511 at a predetermined interval. In addition, a lens 132 on which light from the point light source 130 enters is disposed inside the illumination unit 511. The lens 132 may be attached to the point light source 130 or may be supported by other methods.

  In addition, the illumination unit 511 includes a diffusion plate 133 that diffuses light from the lens 132 at the top. Note that the diffusion plate 133 has a planar shape and is disposed substantially parallel to the substrate normal direction 115.

  Next, light emitted from the point light source 130 will be described. The light emitted from the point light source 130 is emitted by the lens 132 in two directions mainly having a polar angle θ from the substrate normal direction 115 when viewed from the cross section of the liquid crystal display unit 110 as shown in FIG. Is done.

  Light emitted from the lens 132 enters the diffusion plate 133 and is diffused by the diffusion plate 133. Therefore, the emitted light 113 is emitted in all azimuth angles unlike the above-described embodiment and the first to third modifications. Therefore, the traveling direction of the emitted light 113 from the illumination unit 511 has a certain extent, but is within the range applicable in the present invention.

  As described above, the light from the illumination unit 511 is emitted in all azimuth angles. Therefore, in order to obtain good bright display and dark display, the configuration of the liquid crystal display unit 510 is different from that of the above embodiment. Hereinafter, the configuration of the liquid crystal display unit 510 in this modification will be described. In addition, the same code | symbol is attached | subjected to the element same or equivalent to the said embodiment, and the overlapping description is abbreviate | omitted.

  FIG. 19 is a diagram for explaining a configuration of a liquid crystal display unit in the present modification. As illustrated in FIG. 19, the liquid crystal display unit 510 includes a first birefringent film 134 between the first substrate 105 and the first polarizing plate 108, and the second substrate 106 Between the second polarizing plate 109, a second birefringent film 135 and an optical phase compensation film 136 are provided in this order from the bottom in FIG. In this modification, the light direction conversion unit 112 is formed of a sheet that collects light incident from all directions, for example, a lens sheet.

  As described above, since the light from the illumination unit 511 is emitted in all azimuth angles, the light incident on the liquid crystal layer 107 needs to be affected by the effective retardation of the liquid crystal layer 107 in all azimuth angles. For this purpose, the incident light to the liquid crystal layer 107 is converted into clockwise or counterclockwise circularly polarized light by the first birefringent film 134. Next, by setting the effective retardation of the liquid crystal layer 107 to λ / 2, the transmitted light of the liquid crystal layer 107 is made to be counterclockwise or clockwise circularly polarized light. Finally, the circularly polarized light may be converted to linearly polarized light by the second birefringent film 135.

  The birefringent film used here is generally called a λ / 4 plate, but is preferably optimized by the emission angle θ of the illumination unit 511. For example, when a general film having a refractive index of about 1.5 is used, it is desirable that 100 nm ≦ Re ≦ 150 nm with respect to incident light having a wavelength of 550 nm. In this modification, as an example, a plate with Nz = 0.5 and Re = 137 nm used as a wide viewing angle λ / 4 plate is used.

  Here, the Nz coefficient is defined as Nz = (nx−nz) / (nx−ny) where the in-plane main refractive index is nx and ny (nx ≧ ny), and the refractive index in the thickness direction is nz. Re is defined as Re = (nx−ny) d, where d is the thickness of the optical phase compensation film.

  Next, the operation in the liquid crystal display unit 510 will be described. At the time of dark display, birefringence does not occur in the liquid crystal layer 107. Therefore, the first and second birefringent films 134 and 135 generate opposite polarization states and return to the original linearly polarized light. Dark display equivalent to that when the pair of polarizing plates is viewed obliquely is possible.

However, as described above, the polarizing plate absorption axis crossing angle depends on the azimuth angle and polar angle in the traveling direction of incident light. As described above, since it is necessary to consider all azimuth angles in this modification, the polarizing plate absorption axis crossing angle when viewed from the substrate normal direction 115 is φ _P = 90 ° in consideration of symmetry. To do. Further, in order to compensate the azimuth angle dependency of the polarizing plate transmittance, the optical phase compensation film 136 is disposed as described above.

  For the characteristics of the optical phase compensation film 136, various methods have been proposed including a method of combining a plurality of optical phase compensation films. In this modification, for example, the Nz coefficient at an incident light wavelength of 550 nm is 0.5. , One film of Re = 275 nm is used. Note that when this method is used, the characteristics equivalent to those of this modification can be realized as long as 0.4 ≦ Nz coefficient ≦ 0.6 and 240 nm ≦ Re ≦ 300 nm with respect to the incident light wavelength of 550 nm.

  In FIG. 19, the optical phase compensation film 136 is arranged between the second birefringent film 135 and the second polarizing plate 109, but the first birefringent film 134 and the second birefringent film 134 are arranged. One polarizing plate 108 may be disposed.

  FIG. 20 is a diagram showing an example of an axial arrangement of a polarizing plate or the like that enables the above-described action, and shows an axial arrangement when viewed from the substrate normal direction 115. In FIG. 20, arrows 217 and 218 indicate the absorption axes of the first polarizing plate 108 and the second polarizing plate 109, the arrow 237 indicates the slow axis of the first birefringent film 134, and the arrow 238 indicates the absorption axis. The slow axis of the 2nd birefringent film 135 is shown. The axial arrangement of the first and second birefringent films 134 and 135 may be reversed. The slow axis of the optical phase compensation film 136 is parallel to the x axis or the y axis.

  In the liquid crystal display panel configured as described above, the result of obtaining the transmittance for each of bright display and dark display is shown in FIG. In addition, the said result made the output angle (theta) of the emitted light from the illumination part in the air 60 degrees, and calculated | required the azimuth angle dependence.

  As shown in FIG. 21, in all directions, the transmittance during bright display is high, and the transmittance during dark display is low. Further, at θ = 60 °, the transmittance during bright display is about 24%, and a value almost equal to that in the above embodiment can be obtained.

  As described above, similarly to the above-described embodiment and the like, according to this modification, an electric field can be uniformly applied to the liquid crystal layer during bright display, and a liquid crystal display panel having a liquid crystal layer with high transmittance can be realized. can do. In addition, since the cell gap can be reduced, the liquid crystal layer can have a high transmittance and can be driven with a low driving voltage. In addition, the material cost of the liquid crystal layer can be reduced, and as a result, a highly productive liquid crystal display panel can be provided.

  The present invention is not limited to the above-described embodiment or modifications 1 to 5, and various modifications are possible. For example, it can be replaced with a configuration that is substantially the same as the configuration described in the above embodiment or modifications 1 to 5, a configuration that exhibits the same operational effects, or a configuration that can achieve the same purpose.

  For example, as an alternative to the liquid crystal layer 107, an electro-optic crystal typified by potassium tantalate niobate may be used. In the above-described embodiment and Modifications 1 to 5, the liquid crystal display panel using an isotropic liquid crystal material for the liquid crystal layer 107 has been described. However, the present invention can also be applied to a liquid crystal display panel using a nematic liquid crystal material. Needless to say, the above-described embodiment and Modifications 1 to 5 can be applied in combination as long as they do not contradict each other.

For example, the isotropic liquid crystal material and the electro-optic crystal correspond to the medium in the claims.

  100, 800 Liquid crystal display panel, 101, 801 Pixel electrode, 102, 802 Common electrode, 103 803 Electrical wiring, interlayer insulating film, etc. 104, 804 Color filter, 105 First substrate, 106 Second substrate, 107, 807 Liquid crystal layer, 108 first polarizing plate, 109 second polarizing plate, 110 liquid crystal display unit, 111 illumination unit, 112 light direction changing unit, 113 outgoing light, 115 substrate normal direction, 124 light guide plate, 125 fluorescent tube, 126 reflector, 127 reverse prism sheet, 128 Mie scattering sheet, 129 groove, 133 diffuser plate, 139, 140 antireflection film, 134 first birefringent film, 135 second birefringent film, 136 optical phase compensation Film, 805, 806 Transparent substrate.

Claims (20)

A pair of substrates;
A medium that is disposed between the pair of substrates and produces optical isotropy when no voltage is applied, and optical anisotropy when a voltage is applied;
A pixel electrode formed on one of the pair of substrates, a common electrode formed on the other,
An illumination unit that emits light to the medium,
The display unit, wherein the illuminating unit causes the light to enter the medium obliquely with respect to a direction from the one substrate to the other substrate.   The display panel further includes a light direction conversion unit that converts the direction of the light that has passed through the pair of substrates and the medium from the illumination unit to a direction from the one substrate to the other substrate. The display panel according to claim 1, characterized in that:   The display panel according to claim 1, wherein the light is light having maximum luminance among light emitted from the illumination unit.   The display panel according to claim 1, wherein each of the pair of substrates has a polarizing plate on a surface far from the medium.   2. The display according to claim 1, wherein the illuminating unit makes the light incident at an angle of 40 degrees or more and less than 90 degrees in the air with respect to a direction from the one substrate to the other substrate. panel.   When the potential difference between the pixel electrode and the common electrode is zero, the medium has a three-dimensional refractive index substantially isotropic, and when the potential difference is generated between the pixel electrode and the common electrode, the electro-optic effect 2. The display panel according to claim 1, wherein the display panel has a property of inducing refractive index anisotropy. The illumination unit is
At least one light source;
A light guide plate that is arranged alongside the light source and guides light from the at least one light source;
2. The display panel according to claim 1, wherein surfaces of the light guide plate far from the pair of substrates are inclined at an angle of 1 ° or more with respect to a direction parallel to the pair of substrates. The distance between the pixel electrode and the common electrode is d (nm),
An electric field in a direction from the one substrate applied to the medium to the other substrate is E,
The refractive index when E of the medium is 0 is n ₀ ,
A proportionality constant proportional to the refractive index of the medium, k,
The refractive index of the medium in the normal direction of the substrate is n ₀ + kE ² ,
When
Expressed in the medium

2. The display panel according to claim 1, wherein an effective retardation R ′ represented by the formula is 240 nm ≦ R ′ ≦ 310 nm with respect to a wavelength of 550 nm of the light. When viewed from the direction from the one substrate to the other substrate, the smaller angle φ _P among the angles formed by the absorption axes of the respective polarizing plates is 60 ° ≦ φ _P ≦ 88 °. ,
The display panel according to claim 1, wherein the light direction forms an angle of φ _P / 2 with the absorption axis of each polarizing plate. When the refractive index of the polarizing plate polarizing layer is n _P , the angle φ _P is

The display panel according to claim 9, wherein: The display panel further includes:
A birefringent film disposed between each of the polarizing plates and the medium;
The illumination unit emits the light in all directions as seen from the direction from the one substrate to the other substrate,
The absorption axes of the polarizing plates are orthogonal to each other,
The slow axes of the birefringent films are perpendicular to each other,
The smaller angle formed by one of the absorption axes of each polarizing plate and the slow axis of each birefringent film is 45 °,
The display panel according to claim 1, wherein the retardation of each birefringent film is 100 nm or more and 150 nm or less with respect to the light having a wavelength of 550 nm.   The display panel according to claim 11, wherein each of the birefringent films has an Nz coefficient of 0.4 to 0.6. The display panel further includes an optical phase compensation film between one of the polarizing plates adjacent to each other and one of the birefringent films,
The optical phase compensation film is
Nz coefficient is 0.4 or more and 0.6 or less,
Retardation is 240 nm or more and 300 nm or less for the light having a wavelength of 550 nm,
The one of the absorption axes of each polarizing plate and the slow axis of the optical phase compensation film are parallel or orthogonal to each other when viewed from the direction from the one substrate to the other substrate. Display panel.   The display panel according to claim 1, wherein the light beam direction conversion unit is a prism sheet. The light beam direction conversion unit is
A prism sheet,
The display panel according to claim 1, further comprising a scattering sheet that scatters light emitted from the prism sheet. The scattering sheet has a plurality of particles scattered inside,
When the average diameter of the scattering particles is L (nm),
0.4 <πL / 550 <3
The display panel according to claim 15, wherein the display panel is a display panel.   The display panel according to claim 4, wherein each of the polarizing plates has an antireflection film on a surface far from the medium. When the refractive index for light having a wavelength of 550 nm of the antireflection film is n _R and the film thickness is d _R nm,
1 ≦ n _R <1.5,

The display panel according to claim 17, wherein: The illumination unit is
Multiple point sources,
A lens that causes the light from each of the point light sources to enter the medium at the predetermined angle with respect to a direction from the one substrate to the other substrate;
A diffusion unit for diffusing light from the lens;
The display panel according to claim 11, further comprising:   The display panel according to claim 1, wherein the medium is a liquid crystal that exhibits optical isotropy when no voltage is applied and also exhibits optical anisotropy when a voltage is applied.

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