JP2014102521A - Liquid crystal device and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal device and electronic equipment capable of compensating a viewing angle while considering retardation of a protective film of a polarizing plate.SOLUTION: A liquid crystal device 1 includes a liquid crystal panel 2, polarizing plates 6, 7 disposed to interpose the liquid crystal panel 2, and a retardation film 8 disposed between the polarizing plate 6 or the polarizing plate 7 and the liquid crystal panel 2. The polarizing plates 6, 7 include polarizers 6a, 7a and light-transmitting protective films 6b, 7b interposing the polarizers 6a, 7a, respectively. An in-plane retardation Re(nm) of the protective films 6b, 7b satisfies 0≤Re≤5; a thickness direction retardation Rth (nm) of the protective films 6b, 7b satisfies 20<Rth≤40; an in-plane retardation Re(nm) of the retardation film 8 satisfies 100≤Re≤150; a Nz value of the retardation film 8 satisfies 0.2≤Nz≤0.4; and an average refractive index Nave of the retardation film 8 satisfies 1.4≤Nave≤2.0.

Description

  One embodiment of the present invention relates to a liquid crystal device and an electronic device.

  A liquid crystal device generally includes a liquid crystal panel having a pair of substrates and a liquid crystal layer sealed between these substrates, and further has a polarizing plate outside the liquid crystal panel. As one of the liquid crystal devices, there are known an IPS (In Plane Switching) mode and FFS (Fringe Field Switching) mode liquid crystal device in which a liquid crystal layer is driven by an electric field (lateral electric field) parallel to the substrate. In these lateral electric field type liquid crystal devices, a configuration is known in which a retardation film is disposed between a liquid crystal panel and a polarizing plate in order to widen the viewing angle. In particular, Patent Document 1 proposes a retardation film condition that takes into account the retardation of the transparent protective film contained in the polarizing plate.

JP 2004-157523 A

  However, in the conventional compensation conditions including the above-mentioned Patent Document 1, the average refractive index of the retardation film is not taken into consideration, and a wide viewing angle may not be obtained depending on the average refractive index of the retardation film. There is.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.
[Application Example 1]
A liquid crystal panel having a pair of substrates and a liquid crystal layer disposed between the pair of substrates and driven by an electric field having a component parallel to the substrates; a first polarizing plate disposed with the liquid crystal panel interposed therebetween; A second polarizing plate, and a retardation film disposed between the first polarizing plate and the liquid crystal panel, or between the second polarizing plate and the liquid crystal panel. The polarizing plate 2 has a polarizer and a translucent protective film sandwiching the polarizer, and the in-plane retardation Re ₁ of the protective film satisfies 0 nm ≦ Re ₁ ≦ 5 nm, and the thickness direction of the protective film The retardation Rth satisfies 20 nm <Rth ≦ 40 nm, the in-plane retardation Re ₂ of the retardation film satisfies 100 nm ≦ Re ₂ ≦ 150 nm, and the Nz value of the retardation film is 0.2 ≦ Nz ≦ 0. 4 and the average refractive index Nav of the retardation film e is a liquid crystal device satisfying 1.4 ≦ Nave ≦ 2.0.

According to such a configuration, the in-plane retardation Re ₁ and the thickness direction retardation of the protective film can be selected by appropriately selecting the in-plane retardation Re ₂ , Nz value, and average refractive index Nave of the retardation film. A liquid crystal device capable of displaying with a high contrast ratio (that is, a wide viewing angle) over a wide angle range by compensating Rth can be obtained.

In this specification, the in-plane retardation Re ₁ of the protective film is the x-axis in the direction in which the in-plane refractive index of the protective film is maximum, the y-axis in the direction parallel to the surface of the protective film and perpendicular to the x-axis. Re ₁ = (nx ₁ −ny) where z is the thickness direction of the film, nx ₁ , ny ₁ , nz ₁ are the refractive indexes at 550 nm in the respective axial directions, and d ₁ is the thickness of the protective film. ₁ ) represented by d ₁ The thickness direction retardation Rth of the protective film is represented by Rth = {(nx ₁ + ny ₁ ) / 2−nz ₁ } d ₁ . On the other hand, the in-plane retardation Re ₂ of the retardation film is such that the direction in which the in-plane refractive index of the retardation film is maximum is the x-axis, the direction parallel to the plane of the retardation film and perpendicular to the x-axis is the y-axis, Re ₂ = (nx ₂ ) where z is the thickness direction of the retardation film, nx ₂ , ny ₂ , nz ₂ are the refractive indices at 550 nm in each axial direction, and d ₂ is the thickness of the retardation film. represented by -ny ₂₎ d _2. Further, Nz value of the retardation film is represented by _{Nz = (nx 2 -nz 2)} / (nx 2 -ny 2). The average refractive index Nave of the retardation film is expressed by Nave = (nx ₂ + ny ₂ + nz ₂ ) / 3.

[Application Example 2]
A liquid crystal panel having a pair of substrates and a liquid crystal layer disposed between the pair of substrates and driven by an electric field having a component parallel to the substrates; a first polarizing plate disposed with the liquid crystal panel interposed therebetween; A second polarizing plate, and a retardation film disposed between the first polarizing plate and the liquid crystal panel, or between the second polarizing plate and the liquid crystal panel. The polarizing plate 2 has a polarizer and a translucent protective film sandwiching the polarizer, and the in-plane retardation Re ₁ of the protective film satisfies 0 nm ≦ Re ₁ ≦ 5 nm, and the thickness direction of the protective film The retardation Rth satisfies 40 nm <Rth ≦ 60 nm, the in-plane retardation Re ₂ of the retardation film satisfies 100 nm ≦ Re ₂ ≦ 150 nm, and the Nz value of the retardation film is −0.1 ≦ Nz <0. 2 and the average refractive index Na of the retardation film ve is a liquid crystal device satisfying 1.4 ≦ Nave ≦ 2.0.

According to such a configuration, the in-plane retardation Re ₁ and the thickness direction retardation of the protective film can be selected by appropriately selecting the in-plane retardation Re ₂ , Nz value, and average refractive index Nave of the retardation film. A liquid crystal device capable of displaying with a high contrast ratio (that is, a wide viewing angle) over a wide angle range by compensating Rth can be obtained.

[Application Example 3]
In the liquid crystal device, the retardation film is disposed between the liquid crystal panel and the first polarizing plate, and the slow axis of the retardation film and the absorption axis of the second polarizing plate are alignment directions of the liquid crystal layer. And the absorption axis of the first polarizing plate is perpendicular to the alignment direction of the liquid crystal layer.

With such a configuration, display characteristics with a wide viewing angle can be realized in an E-mode liquid crystal device.
[Application Example 4]
In the liquid crystal device, the retardation film is disposed between the liquid crystal panel and the second polarizing plate, and the slow axis of the retardation film and the absorption axis of the first polarizing plate are alignment directions of the liquid crystal layer. And the absorption axis of the second polarizing plate is perpendicular to the alignment direction of the liquid crystal layer.

According to such a configuration, display characteristics with a wide viewing angle can be realized in an O-mode liquid crystal device.
[Application Example 5]
The liquid crystal device, wherein the liquid crystal panel is an IPS mode liquid crystal panel.

According to such a configuration, an IPS mode liquid crystal device having display characteristics with a wide viewing angle can be obtained.
[Application Example 6]
The liquid crystal device, wherein the liquid crystal panel is an FFS mode liquid crystal panel.

According to such a configuration, an FFS mode liquid crystal device having display characteristics with a wide viewing angle can be obtained.
[Application Example 7]
Electronic equipment comprising the liquid crystal device in a display portion.

  According to such a configuration, an electronic device capable of performing display with a wide viewing angle on the display unit can be obtained.

2A and 2B show a configuration of a liquid crystal device, in which FIG. 1A is a perspective view, FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A, and FIG. The enlarged plan view of a pixel area. FIG. 6 is an equivalent circuit diagram of various elements, wirings, and the like in a plurality of sub-pixels constituting a pixel region. The top view which extracts and shows the part corresponding to one sub pixel among element substrates. Sectional drawing in the position of the BB line in FIG. The schematic diagram which shows the direction of a polarizing plate and retardation film. The figure which shows the viewing angle characteristic of a liquid crystal device at the time of changing the average refractive index Nave of a phase difference film in each Example and a reference example. The O mode liquid crystal device which concerns on the modification 1 is shown, (a) is a perspective view, (b) is sectional drawing in the CC line in (a). The schematic diagram which shows the orientation direction of a liquid crystal layer, and the direction of a polarizing plate and retardation film in an O mode liquid crystal device. The top view which extracts and shows the part corresponding to one sub pixel among the element substrates of the liquid crystal device to which FFS mode is applied. Sectional drawing in the position of the DD line in FIG. The perspective view of the mobile telephone as an electronic device.

  Hereinafter, embodiments of a liquid crystal device and an electronic device will be described with reference to the drawings. In the drawings shown below, the dimensions and ratios of the components are appropriately different from the actual ones in order to make the components large enough to be recognized on the drawings.

  1A and 1B show a configuration of the liquid crystal device 1, wherein FIG. 1A is a perspective view, FIG. 1B is a cross-sectional view taken along the line AA in FIG. 1A, and FIG. FIG. The liquid crystal device 1 includes a liquid crystal panel 2 and a polarizing plate 6 as a first polarizing plate and a polarizing plate 7 as a second polarizing plate, which are disposed with the liquid crystal panel 2 interposed therebetween. A retardation film 8 is disposed between the polarizing plate 6 and the liquid crystal panel 2.

  The liquid crystal panel 2 includes an element substrate 10 and a counter substrate 20 as a pair of substrates bonded to each other with a frame-shaped sealing material 58 therebetween. A liquid crystal layer 50 is sealed in a space surrounded by the element substrate 10, the counter substrate 20, and the sealing material 58. The element substrate 10 is larger than the counter substrate 20, and is bonded in a state in which a part thereof protrudes from the counter substrate 20. A driver IC 57 for driving the liquid crystal layer 50 is mounted on the protruding portion. The polarizing plate 6 is disposed on the element substrate 10 side of the liquid crystal panel 2, and the polarizing plate 7 is disposed on the counter substrate 20 side of the liquid crystal panel 2. Therefore, the polarizing plate 7, the liquid crystal panel 2, the retardation film 8, and the polarizing plate 6 are laminated in this order, and these elements are bonded via an adhesive layer.

  As shown in FIG. 1C, the polarizing plate 6 includes a polarizer 6a and a pair of translucent protective films 6b bonded to both surfaces of the polarizer 6a. Similarly, the polarizing plate 7 includes a polarizer 7a and a pair of protective films 7b having translucency bonded to both surfaces of the polarizer 7a.

As the polarizers 6a and 7a, for example, a uniaxially stretched film obtained by adsorbing a dichroic substance such as iodine or a dichroic dye on a polyvinyl alcohol film can be used.
The protective films 6b and 7b are particularly limited to those having an in-plane retardation Re ₁ of 10 nm or less, more preferably 5 nm or less, and a thickness direction retardation Rth of 0 nm to 100 nm, more preferably 0 nm to 60 nm. Can be used. Examples of the material constituting the protective films 6b and 7b include cellulose polymers such as triacetyl cellulose (TAC) and diacetyl cellulose, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, acrylic polymers such as polymethyl methacrylate, Styrene polymers such as polystyrene and acrylonitrile / styrene copolymer (AS resin), polycarbonate polymers and the like can be used. Polyolefin polymers, vinyl chloride polymers, amide polymers, imide polymers, sulfone polymers, and the like may also be used. Alternatively, the protective films 6b and 7b can be formed as a cured layer of a thermosetting or ultraviolet curable resin such as acrylic, urethane, acrylic urethane, epoxy, or silicone. Of these materials, triacetyl cellulose is preferred.

In the above, the in-plane retardation Re ₁ of the protective films 6b and 7b is such that the direction in which the in-plane refractive index of the protective films 6b and 7b is maximum is the x axis, parallel to the surfaces of the protective films 6b and 7b and perpendicular to the x axis. , The refractive index at 550 nm in each axial direction is nx ₁ , ny ₁ , nz ₁ , and the thicknesses of the protective films 6 b, 7 b are d _1. In this case, Re ₁ = (nx ₁ −ny ₁ ) d ₁ . The thickness direction retardation Rth of the protective films 6b and 7b is represented by Rth = {(nx ₁ + ny ₁ ) / 2−nz ₁ } d ₁ .

The retardation film 8 has an Nz value of −0.1 or more and 0.8 or less, an in-plane retardation Re ₂ of 50 nm or more and 400 nm or less, more preferably 100 nm or more and 300 nm or less, and an average refractive index Nave. What is 1.4 or more and 2.0 or less can be used without particular limitation. For example, a birefringent film of a polymer film or an alignment film of a liquid crystal polymer can be used. Examples of the high molecular polymer include triacetyl cellulose (Nave = 1.48), zeonore (Nave = 1.52), polycarbonate (Nave = 1.59), PMMA (Nave = 1.49), polystyrene (Nave = 1.59) can be used.

In the above, the in-plane retardation Re ₂ of the retardation film 8 is the direction in which the in-plane refractive index of the retardation film 8 is maximum, the x axis, the direction parallel to the surface of the retardation film 8 and the direction perpendicular to the x axis. When the thickness direction of the y-axis and retardation film 8 is the z-axis, the refractive index at 550 nm in each axial direction is nx ₂ , ny ₂ , nz ₂ , and the thickness of the retardation film 8 is d ₂ , Re ₂ = (nx ₂ −ny ₂ ) d ₂ Further, Nz value of the retardation film 8 is represented by _{Nz = (nx 2 -nz 2)} / (nx 2 -ny 2). The average refractive index Nave of the retardation film 8 is represented by Nave = (nx ₂ + ny ₂ + nz ₂ ) / 3.

  Next, the configuration of the liquid crystal panel 2 will be described in detail. A large number of subpixels 4R, 4G, and 4B (FIG. 2) that contribute to display are arranged in a matrix in a region of the liquid crystal panel 2 in which the liquid crystal layer 50 is sealed. Hereinafter, an area composed of a set of sub-pixels 4R, 4G, and 4B is also referred to as a pixel area 5.

  FIG. 2 is an enlarged plan view of the pixel region 5. In the pixel area 5, a large number of rectangular sub-pixels 4R, 4G, and 4B are arranged. The sub-pixels 4R, 4G, and 4B contribute to displaying any one of red, green, and blue, respectively. Hereinafter, the subpixels 4R, 4G, and 4B are also simply referred to as subpixels 4 when colors are not distinguished. The sub-pixels 4R, 4G, and 4B are provided with color filters 23 (FIG. 5) corresponding to red, green, and blue, respectively. The color filter 23 can make the transmitted light have a predetermined color by absorbing a specific wavelength component of the incident light. A light shielding layer 22 formed in the same layer as the color filter 23 is disposed between the adjacent sub-pixels 4.

  The sub-pixels 4 are arranged in a matrix, and the colors of the sub-pixels 4 arranged in a certain column are all the same. In other words, the sub-pixels 4 are arranged so that corresponding colors are arranged in a stripe pattern. Further, the pixel 3 is configured by a set of three adjacent sub-pixels 4R, 4G, and 4B arranged in the row direction. The pixel 3 is a minimum unit (pixel) for display. In each pixel 3, display of various colors can be performed by adjusting the luminance balance of the sub-pixels 4R, 4G, and 4B.

  FIG. 3 is an equivalent circuit diagram of various elements, wirings, and the like in the plurality of subpixels 4 constituting the pixel region 5. In the pixel region 5, the plurality of scanning lines 12 and the plurality of data lines 13 are wired so as to intersect with each other, and the TFT (Thin Film Transistor) element 30, A sub-pixel 4 including the pixel electrode 16 is formed. The pixel electrode 16 is electrically connected to the drain region of the TFT element 30. A common electrode 18 is disposed in the subpixel 4. Each common electrode 18 is kept at an equal potential via a common line 18a.

  The TFT element 30 is turned on by an ON signal included in the scanning signals G1, G2,..., Gm supplied from the scanning line 12. At this time, the image signals S1, S2,. Supply to the electrode 16. When the electric field according to the potential difference between the pixel electrode 16 and the common electrode 18 is applied to the liquid crystal layer 50, the alignment state of the liquid crystal layer 50 changes. Thereby, the polarization conversion function of the liquid crystal panel 2 can be brought into a desired state.

  Next, the constituent elements of the sub-pixel 4 will be described in detail with reference to FIGS. FIG. 4 is a plan view showing an extracted portion corresponding to one subpixel 4 in the element substrate 10. 5 is a cross-sectional view taken along the line BB in FIG. In the following description, “upper layer” or “lower layer” refers to a layer formed relatively above or below in FIG.

  As shown in FIG. 4, in each sub-pixel 4, the scanning line 12 and the data line 13 are arranged so as to intersect with each other, and a TFT element 30 is formed corresponding to the intersection. In this specification, the extending direction of the scanning lines 12 is defined as the X direction, and the extending direction of the data lines 13 is defined as the Y direction. Each sub-pixel 4 is formed with a pixel electrode 16 and a common electrode 18 having a comb-like portion. Among these, the pixel electrode 16 is electrically connected to the drain electrode 33 of the TFT element 30. The common electrode 18 is formed integrally with the common line 18a, and is electrically connected to the common electrode 18 of the adjacent subpixel 4 via the common line 18a. The pixel electrode 16 and the common electrode 18 are arranged to face each other in a state in which comb-shaped portions are alternately inserted.

Subsequently, a cross-sectional structure of the sub-pixel 4 will be described with reference to FIG. A scanning line 12 is formed on the surface of the glass substrate 11 facing the glass substrate 21. A capacitance line that forms a capacitance with the drain electrode 33 may be formed in the same layer as the scanning line 12. An insulating layer made of silicon oxide (SiO ₂ ) or the like may be provided between the glass substrate 11 and the scanning line 12. A semiconductor layer 31 is formed on the scanning line 12 with a gate insulating layer 42 made of silicon oxide (SiO ₂ ) or the like interposed therebetween. The semiconductor layer 31 can be made of amorphous silicon, for example. Further, the source electrode 13 a and the drain electrode 33 are formed so as to partially overlap the semiconductor layer 31. The source electrode 13a is formed integrally with the data line 13 (FIG. 4). The TFT element 30 is composed of the semiconductor layer 31, the source electrode 13a, the drain electrode 33, the scanning line 12, and the like. The scanning line 12 also serves as a gate electrode of the TFT element 30. The scanning line 12 (gate electrode), source electrode 13a (data line 13), and drain electrode 33 are, for example, titanium (Ti), chromium (Cr), tungsten (W), tantalum (Ta), molybdenum (Mo), aluminum. It can be composed of a metal simple substance, an alloy, a metal silicide, a polysilicide, a laminate of these, or conductive polysilicon containing at least one of metals such as (Al).

A pixel electrode 16 made of light-transmitting ITO (Indium Tin Oxide) and a common electrode 18 are formed on the TFT element 30 with an interlayer insulating layer 43 made of silicon oxide (SiO ₂ ) or the like interposed therebetween. . In the cross section of FIG. 5, the common electrode 18 and the pixel electrode 16 are alternately arranged with comb-like portions of the electrode. Among these, the pixel electrode 16 is electrically connected to the drain electrode 33 of the TFT element 30 through a contact hole 34 provided in the interlayer insulating layer 43. Thus, the pixel electrode 16 and the common electrode 18 are formed on the surface of the glass substrate 11 that faces the glass substrate 21.

  An alignment film 48 made of polyimide is formed on the pixel electrode 16 and the common electrode 18. The alignment film 48 is a member in contact with the liquid crystal layer 50. By rubbing the alignment film 48, the liquid crystal molecules 51 of the liquid crystal layer 50 can be aligned along the rubbing direction. In the present embodiment, the alignment film 48 is rubbed along the +95 degree direction. In this specification, the rubbing direction or the alignment direction of the liquid crystal molecules 51 is counterclockwise about the Z axis when the XY plane is viewed from the positive direction of the Z axis and the positive direction of the X axis is 0 degrees. It is represented by an azimuth angle in which the counterclockwise direction is positive. The element substrate 10 includes elements from the glass substrate 11 to the alignment film 48.

  On the other hand, a color filter 23 and an alignment film 28 are laminated in this order on the surface of the glass substrate 21 that faces the glass substrate 11. More specifically, the layer in which the color filter 23 is formed includes three types of color filters 23 corresponding to red, green, and blue, and a light shielding layer 22 disposed between the color filters 23 of these colors (FIG. 2). ) And are formed. The alignment film 28 is made of polyimide and has the same properties as the alignment film 48 on the element substrate 10 side. In this embodiment, the alignment film 28 is rubbed along the direction of −95 degrees. Therefore, the rubbing directions of the alignment films 28 and 48 are parallel and opposite to each other. The counter substrate 20 is composed of elements from the glass substrate 21 to the alignment film 28.

  A liquid crystal layer 50 having liquid crystal molecules 51 is disposed in a region between the element substrate 10 and the counter substrate 20, that is, a region sandwiched between the alignment film 28 and the alignment film 48. Δnd of the liquid crystal layer 50 (product of the birefringence Δn of the liquid crystal molecules 51 and the thickness d of the liquid crystal layer 50) can be set, for example, between 300 nm and 400 nm. In this embodiment, the thickness is 360 nm.

  The liquid crystal molecules 51 of the liquid crystal layer 50 are aligned in the rubbing direction of the alignment films 28 and 48, that is, in the direction of 95 degrees when no voltage is applied (including a state where a weak voltage corresponding to the off state is applied. The same applies hereinafter). Orient along. Since the rubbing directions of the alignment films 28 and 48 are parallel and opposite as described above, the liquid crystal layer 50 has a so-called anti-parallel alignment. Accordingly, at least some of the liquid crystal molecules 51 of the liquid crystal layer 50 are aligned in parallel to the glass substrate 11 regardless of the magnitude of the drive voltage (the magnitude of the electric field).

  FIG. 6 is a schematic diagram showing the orientation of the polarizing plates 6 and 7 and the retardation film 8. In FIG. 6, the direction of the alignment direction 50A of the liquid crystal layer 50, the absorption axes 6A and 7A of the polarizing plates 6 and 7, and the direction of the slow axis 8A of the retardation film 8 are indicated by arrows. Here, the slow axis 8A of the retardation film 8 and the absorption axis 7A of the polarizing plate 7 are parallel to the alignment direction 50A of the liquid crystal layer 50, and the absorption axis 6A of the polarizing plate 6 is the alignment direction 50A of the liquid crystal layer 50. Is orthogonal. Therefore, the direction of the slow axis 8A and the absorption axis 7A is 95 degrees as in the orientation direction 50A, and the direction of the absorption axis 6A is 5 degrees. The liquid crystal device 1 having such a configuration is called an E mode.

  The liquid crystal device 1 performs display by taking out light from a backlight (not shown) or the like incident from the polarizing plate 6 side from the polarizing plate 7 side. Therefore, the observer visually recognizes the display from the polarizing plate 7 side (from the positive direction of the Z axis). The liquid crystal device 1 can perform various displays by modulating incident light by the polarization conversion function of the liquid crystal panel 2 and the polarization selection function of the polarizing plates 6 and 7.

  Next, the operation of the liquid crystal device 1 having the above configuration will be described. During the operation of the liquid crystal device 1, the common electrode 18 is maintained at a predetermined common potential, while an image signal is written to the pixel electrode 16 via the data line 13 and the TFT element 30. Thereby, a driving voltage corresponding to the magnitude of the image signal is applied between the common electrode 18 and the pixel electrode 16. When a driving voltage is applied and a potential difference is generated, an electric field having electric lines of force that exit from the surface of the pixel electrode 16 and reach the surface of the common electrode 18 is generated. At this time, an electric field (lateral electric field) parallel to the glass substrate 11 is generated above the common electrode 18 and the pixel electrode 16, that is, in the layer where the liquid crystal layer 50 is disposed. In other words, the electric field has a component parallel to the glass substrate 11. The direction of the lateral electric field in plan view is a direction orthogonal to the extending direction of the comb-like electrodes of the common electrode 18 and the pixel electrode 16. The liquid crystal molecules 51 contained in the liquid crystal layer 50 change the alignment direction in a plane parallel to the glass substrate 11 in accordance with the magnitude of the lateral electric field. Here, the alignment direction of the liquid crystal molecules 51 when no voltage is applied and the direction of the transverse electric field generated when the voltage is applied (the direction orthogonal to the extending direction of the comb-like electrodes of the common electrode 18 and the pixel electrode 16). The angle is about 85 degrees. In this way, the rotation direction of the liquid crystal molecules 51 when a lateral electric field is applied can be made uniform. Thereby, generation | occurrence | production of the domain resulting from the nonuniformity of the said rotation direction can be suppressed.

  When no voltage is applied, the liquid crystal molecules 51 of the liquid crystal layer 50 are aligned along the rubbing direction (95 degrees) of the alignment films 28 and 48. At this time, since the polarization axis of the linearly polarized light transmitted through the polarizing plate 6 is orthogonal to the alignment direction of the liquid crystal molecules 51, the liquid crystal layer 50 is transmitted through the liquid crystal layer 50 while being linearly polarized without being given a phase difference. And is absorbed by the polarizing plate 7. Therefore, when no voltage is applied, display light is not extracted from the polarizing plate 7 and black display is performed.

  On the other hand, when a voltage is applied, the liquid crystal molecules 51 of the liquid crystal layer 50 are driven by a lateral electric field, and the alignment direction changes from 95 degrees. At this time, since the polarization axis of the linearly polarized light transmitted through the polarizing plate 6 is not orthogonal to the alignment direction of the liquid crystal molecules 51, a phase difference is given by the liquid crystal layer 50, and the polarization state changes. The amount of change in the polarization state depends on the retardation (Δnd) of the liquid crystal layer 50 and the rotation angle of the liquid crystal molecules 51. The light that has passed through the liquid crystal layer 50 and has undergone a change in polarization state has a component orthogonal to the absorption axis of the polarizing plate 7 and is incident on the polarizing plate 7, so that part or all of the light passes through the polarizing plate 7. , Visually recognized by an observer. Thus, for example, white display is performed when a voltage is applied.

  When a voltage having an intermediate magnitude between black display and white display is applied, the alignment direction of the liquid crystal molecules 51 changes by an angle corresponding to the magnitude of the voltage. Therefore, the amount of change in polarization state received by transmitted light in the liquid crystal layer 50 changes. Accordingly, the amount of light transmitted through the polarizing plate 7 changes according to the magnitude of the applied voltage, and halftone display is performed.

  Such a liquid crystal mode is called an IPS mode. In the IPS mode, since the liquid crystal molecules 51 are always kept substantially parallel to the glass substrate 11, a change in retardation due to a viewing angle is small, and a wide viewing angle display can be performed.

  Furthermore, in the present embodiment, the retardation film 8 is disposed between the liquid crystal panel 2 and the polarizing plate 6 so that display characteristics with a wider viewing angle can be obtained. The retardation film 8 gives a phase difference to light incident on the polarizing plate 6 in a direction deviated from a predetermined optical axis (Z axis), thereby preventing light leakage when the light is emitted from the polarizing plate 7. Can be reduced. Therefore, the retardation film 8 has a function of compensating for a decrease in contrast when the liquid crystal device 1 is viewed from an oblique direction (a direction having an angle with respect to the Z axis).

  In particular, by appropriately setting the characteristic value of the retardation film 8 according to the characteristic values of the protective films 6b and 7b included in the polarizing plates 6 and 7, a high-contrast display can be obtained over a wider angle range.

Specifically, as the first condition, the in-plane retardation Re ₁ and the thickness direction retardation Rth of the protective films 6b and 7b are 0 nm ≦ Re ₁ ≦ 5 nm.
0nm ≦ Rth ≦ 20nm
In the case of satisfying the above, the in-plane retardation Re ₂ , Nz value, and average refractive index Nave of the retardation film 8 are 200 nm ≦ Re ₂ ≦ 300 nm.
0.4 <Nz ≦ 0.8
1.4 ≦ Nave ≦ 2.0
By setting the value within this range, display characteristics with a wide viewing angle can be obtained.

Further, as the second condition, the in-plane retardation Re ₁ and the thickness direction retardation Rth of the protective films 6b and 7b are 0 nm ≦ Re ₁ ≦ 5 nm.
20 nm <Rth ≦ 40 nm
When satisfying the above, the in-plane retardation Re ₂ , Nz value, and average refractive index Nave of the retardation film 8 are set to 100 nm ≦ Re ₂ ≦ 150 nm.
0.2 ≦ Nz ≦ 0.4
1.4 ≦ Nave ≦ 2.0
By setting the value within this range, display characteristics with a wide viewing angle can be obtained.

Further, as the third condition, the in-plane retardation Re ₁ and the thickness direction retardation Rth of the protective films 6b and 7b are 0 nm ≦ Re ₁ ≦ 5 nm.
40 nm <Rth ≦ 60 nm
When satisfying the above, the in-plane retardation Re ₂ , Nz value, and average refractive index Nave of the retardation film 8 are set to 100 nm ≦ Re ₂ ≦ 150 nm.
−0.1 ≦ Nz <0.2
1.4 ≦ Nave ≦ 2.0
By setting the value within this range, display characteristics with a wide viewing angle can be obtained.

  As can be seen from the above examples, the average refractive index Nave of the retardation film 8 is preferably 1.4 ≦ Nave ≦ 2.0 in any condition. By setting the average refractive index Nave to 1.4 or more, the angle range in which high contrast can be obtained can be expanded. Moreover, the retardation film 8 with high reliability about heat resistance etc. is obtained by making average refractive index Nave 2.0 or less.

  In the reference examples and Examples 1 and 2 shown below, it is preferable that the range of the average refractive index Nave is 1.4 or more and 2.0 or less for the first to third conditions described above. It is a specific example shown. FIG. 7 is a diagram illustrating the viewing angle characteristics of the liquid crystal device 1 when the average refractive index Nave of the retardation film is changed in each example and reference example. Specifically, it is a diagram showing the contrast distribution of the display when the observation direction is changed. The center point of each graph corresponds to the normal direction (Z-axis direction) of the liquid crystal panel 2, and the circles having concentric center points have inclinations (polar angles) from the normal direction in ascending order of diameter. It corresponds to directions of 20 degrees (°), 40 degrees, 60 degrees, and 80 degrees. The contour lines in the graph indicate the distribution in the direction in which the contrast is 100 or 500. In each graph, the portion where the contrast is 100 or more at the position of the outer periphery (a line corresponding to a polar angle of 80 degrees) is drawn with a bold line. Therefore, it can be said that the condition where the ratio of the thick line portion in the outer periphery is large is the condition that the wide viewing angle can be obtained.

(Reference example)
In this reference example, as the protective films 6b and 7b, TAC having an in-plane retardation Re ₁ of 0 nm and a thickness direction retardation Rth of 0 nm was used. Further, as the retardation film 8, a film having an in-plane retardation Re ₂ of 270 nm and an Nz value of 0.5 was used. Furthermore, the average refractive index Nave of the retardation film 8 was changed to three of 2.5 / 1.5 / 1.3, and the viewing angle characteristics of the liquid crystal device 1 were obtained for each condition (upper part of FIG. 7).

  As can be seen from FIG. 7, when the average refractive index Nave is 2.5 or 1.5, the contrast at a polar angle of 80 degrees is 100 or more in all directions, and a wide viewing angle characteristic is obtained. . On the other hand, when the average refractive index Nave is set to 1.3, it is confirmed that the contrast at a polar angle of 80 degrees is less than 100 in some orientations, and the viewing angle is narrowed. From the viewpoint of the wide viewing angle, the average refractive index Nave of the retardation film 8 is preferably 1.4 or more.

On the other hand, when the average refractive index Nave is larger than 2.0, the reliability is lowered due to the narrow selection of suitable materials.
Table 1 below shows the chromaticity of black display when viewed from an azimuth angle of 60 degrees and a polar angle of 45 degrees when the average refractive index Nave of the retardation film 8 is changed (CIE color). By degree coordinates). In this reference example, as shown in the upper part of Table 1, when the average refractive index Nave is 2.5 (x = 0.215, y = 0.142), the average refractive index Nave is 1.5 (x = 0.221,0.160), it can be seen that the black chromaticity is bluish. As described above, the average refractive index Nave of the retardation film 8 is preferably set to 2.0 or less from the viewpoint of reliability and chromaticity of black display.

Example 1
In this example, TAC having an in-plane retardation Re ₁ of 0 nm and a thickness direction retardation Rth of 30 nm was used as the protective films 6b and 7b. As the retardation film 8, a film having an in-plane retardation Re ₂ of 130 nm and an Nz value of 0.3 was used. Furthermore, the average refractive index Nave of the retardation film 8 was changed to three of 2.5 / 1.5 / 1.3, and the viewing angle characteristics of the liquid crystal device 1 were obtained for each condition (middle of FIG. 7).

  As can be seen from FIG. 7, when the average refractive index Nave is 1.5, the orientation in which the contrast is 100 or more at a polar angle of 80 degrees is significantly larger than when the average refractive index Nave is 1.3. Increased. On the other hand, if the average refractive index Nave is 2.5, the contrast at a polar angle of 80 degrees reaches 100 in some orientations, but the region where the contrast is 100 or more is greatly reduced. From the viewpoint of wide viewing angle, the average refractive index Nave of the retardation film 8 is preferably 1.4 or more and 2.0 or less.

On the other hand, when the average refractive index Nave is larger than 2.0, the reliability is lowered due to the narrow selection of suitable materials.
According to the middle part of Table 1, in this example, when the average refractive index Nave is 2.5 (x = 0.309, y = 0.208), the average refractive index Nave is 1.5. Compared to (x = 0.348, 0.229), it can be seen that the chromaticity of black becomes bluish. As described above, the average refractive index Nave of the retardation film 8 is preferably set to 2.0 or less from the viewpoint of reliability and chromaticity of black display.

(Example 2)
In this example, TAC having an in-plane retardation Re ₁ of 0 nm and a thickness direction retardation Rth of 50 nm was used as the protective films 6b and 7b. Further, as the retardation film 8, a film having an in-plane retardation Re ₂ of 130 nm and an Nz value of 0.1 was used. Furthermore, the average refractive index Nave of the retardation film 8 was changed to three of 2.5 / 1.5 / 1.3, and the viewing angle characteristics of the liquid crystal device 1 were obtained for each condition (lower part of FIG. 7).

  As can be seen from FIG. 7, when the average refractive index Nave is 1.5, the orientation in which the contrast is 100 or more at the polar angle of 80 degrees is increased as compared with the case where the average refractive index Nave is 1.3. . In particular, when the average refractive index Nave is 1.3, there are six azimuth regions where the polar angle is 80 degrees and the contrast is 100, whereas when the average refractive index Nave is 1.5. Increased to 8 in the same area. On the other hand, if the average refractive index Nave is 2.5, the contrast at a polar angle of 80 degrees reaches 100 in some orientations, but the region where the contrast is 100 or more is greatly reduced. From the viewpoint of wide viewing angle, the average refractive index Nave of the retardation film 8 is preferably 1.4 or more and 2.0 or less.

On the other hand, when the average refractive index Nave is larger than 2.0, the reliability is lowered due to the narrow selection of suitable materials.
According to the lower part of Table 1, in this example, when the average refractive index Nave is 2.5 (x = 0.205, y = 0.119), the average refractive index Nave is 1.5. Compared to (x = 0.329, 0.273), it can be seen that the chromaticity of black is large and bluish. As described above, the average refractive index Nave of the retardation film 8 is preferably set to 2.0 or less from the viewpoint of reliability and chromaticity of black display.

(Electronics)
The liquid crystal device 1 described above can be used by being mounted on an electronic device such as a mobile phone, for example. FIG. 12 is a perspective view of a mobile phone 100 as an electronic device. The mobile phone 100 has a display unit 110 and operation buttons 120. The display unit 110 can display various information including information input by the operation buttons 120 and incoming information by the liquid crystal device 1 incorporated therein. At this time, a wide viewing angle can be displayed on the display unit 110 by the action of the retardation film 8 included in the liquid crystal device 1.

  The liquid crystal device 1 can be used in various electronic devices such as a mobile computer, a digital camera, a digital video camera, an in-vehicle device, and an audio device in addition to the mobile phone 100 described above.

Various modifications can be made to the above embodiment. As modifications, for example, the following can be considered.
(Modification 1)
In the above embodiment, the E-mode liquid crystal device 1 has been described, but the O-mode liquid crystal device 1 may be used. 8A and 8B show an O-mode liquid crystal device 1 according to this modification, in which FIG. 8A is a perspective view and FIG. 8B is a cross-sectional view taken along line CC in FIG. As shown in this figure, in this modification, the retardation film 8 is disposed between the liquid crystal panel 2 and a polarizing plate 7 as a second polarizing plate. FIG. 9 is a schematic diagram showing the orientation direction 50 </ b> A of the liquid crystal layer 50 and the orientations of the polarizing plates 6, 7 and the retardation film 8 in the O-mode liquid crystal device 1. As shown in this figure, the slow axis 8A of the retardation film 8 and the absorption axis 6A of the polarizing plate 6 are parallel to the alignment direction 50A of the liquid crystal layer 50, and the direction is 95 degrees. The absorption axis 7A of the polarizing plate 7 is orthogonal to the alignment direction 50A of the liquid crystal layer 50, and the direction is 5 degrees. The mode of the liquid crystal device 1 having such a configuration is called an O mode. Even in such a configuration, the in-plane retardation Re ₂ , the Nz value, and the average refractive index Nave of the retardation film 8 are appropriately set according to the in-plane retardation Re ₁ and the thickness direction retardation Rth of the protective films 6b and 7b. By setting to a small value (the same value as in the above embodiment), the viewing angle of the liquid crystal device 1 can be widened.

(Modification 2)
The liquid crystal device 1 of each of the above embodiments employs the IPS mode liquid crystal panel 2, but can be replaced with an FFS mode. This modification relates to the liquid crystal device 1 including the liquid crystal panel 2 to which the FFS mode is applied.

  FIG. 10 is a plan view showing an extracted portion corresponding to one subpixel 4 in the element substrate 10 of the liquid crystal panel 2 to which the FFS mode is applied. FIG. 11 is a cross-sectional view taken along the line DD in FIG. In the following, description of components common to FIGS. 4 and 5 is omitted.

  As shown in FIG. 10, a substantially rectangular pixel electrode 16 is electrically connected to the TFT element 30. The pixel electrode 16 is provided with a large number of parallel slits (openings) 16a at equal intervals. The slit 16a has an elongated rectangular shape or a parallelogram, and its long side is inclined at a predetermined angle with respect to the X-axis direction. In this embodiment, the angle is 5 degrees. A common electrode 18 is formed on the lower layer side of the pixel electrode 16. The common electrode 18 is formed at a position overlapping the substantially entire surface of the pixel electrode 16 when viewed from the + Z direction.

As shown in FIG. 11, the common electrode 18 made of ITO is laminated on the TFT element 30 with an interlayer insulating layer 43 made of silicon oxide (SiO ₂ ) or the like interposed therebetween.
A pixel electrode 16 made of ITO is formed on the common electrode 18 with an interlayer insulating layer 44 made of silicon oxide (SiO ₂ ) or the like interposed therebetween. The pixel electrode 16 is provided independently for each sub-pixel 4. The pixel electrode 16 is electrically connected to the drain electrode 33 through a contact hole 34 provided through the interlayer insulating layers 43 and 44. The pixel electrode 16 is provided with a number of slits 16a as described above. Here, the pixel electrode 16, the common electrode 18, and the interlayer insulating layer 44 sandwiched between them also function as a storage capacitor. An alignment film 48 made of polyimide is laminated on the pixel electrode 16.

  In this modification, the alignment films 28 and 48 are rubbed along the direction of 0 degrees. Therefore, the liquid crystal layer 50 has an anti-parallel alignment along the 0 degree direction. Accordingly, in the present modification, the absorption axes of the polarizing plates 6 and 7 and the slow axis of the retardation film 8 are changed to 0 degrees from 95 degrees in the above embodiment or modification. What was 5 degrees is changed to 90 degrees.

  While the common electrode 18 is maintained at a predetermined common potential, an image signal is written to the pixel electrode 16 via the data line 13 and the TFT element 30, so that the common electrode 18 is not connected between the common electrode 18 and the pixel electrode 16. A drive voltage corresponding to the magnitude of the image signal is applied. When a driving voltage is applied and a potential difference is generated, an electric field having electric lines of force that exit from the surface of the pixel electrode 16 and reach the surface of the common electrode 18 is generated. At this time, an electric field (lateral electric field) parallel to the glass substrate 11 is generated in the upper part of the pixel electrode 16, that is, in the layer where the liquid crystal layer 50 is disposed. The direction of the horizontal electric field is a direction orthogonal to the longitudinal direction of the slit 16 a of the pixel electrode 16. The liquid crystal molecules 51 contained in the liquid crystal layer 50 change the alignment direction in a plane parallel to the glass substrate 11 in accordance with the magnitude of the lateral electric field.

The liquid crystal device 1 according to the second modification includes the FFS mode liquid crystal panel 2 described above. Even in such a configuration, the in-plane retardation Re ₂ , the Nz value, and the average refractive index Nave of the retardation film 8 are appropriately set according to the in-plane retardation Re ₁ and the thickness direction retardation Rth of the protective films 6b and 7b. By setting to a small value (the same value as in the above embodiment), the viewing angle of the liquid crystal device 1 can be widened.

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal device, 2 ... Liquid crystal panel, 4 ... Sub pixel, 5 ... Pixel region, 6 ... 1st polarizing plate, 7 ... 2nd polarizing plate, 6A, 7A ... Absorption axis, 6a, 7a ... Polarizer, 6b, 7b ... protective film, 8 ... retardation film, 8A ... slow axis, 10 ... element substrate, 11/21 ... glass substrate, 12 ... scanning line, 13 ... data line, 13a ... source electrode, 16 ... pixel electrode , 16a ... slit, 18 ... common electrode, 18a ... common line, 20 ... counter substrate, 22 ... light shielding layer, 23 ... color filter, 28, 48 ... alignment film, 30 ... TFT element, 31 ... semiconductor layer, 33 ... drain Electrode 34 ... Contact hole 42 ... Gate insulating layer 43 ... 44 Interlayer insulating layer 50 ... Liquid crystal layer 50A ... Orientation direction 51 ... Liquid crystal molecule 57 ... Driver IC 58 ... Sealant 100 ... Electronic equipment As a mobile phone.

Claims (8)

A liquid crystal panel having a pair of substrates and a liquid crystal layer disposed between the pair of substrates and driven by an electric field having a component parallel to the substrates;
A first polarizing plate and a second polarizing plate arranged across the liquid crystal panel;
A retardation film disposed between the first polarizing plate and the liquid crystal panel, or between the second polarizing plate and the liquid crystal panel,
The first polarizing plate and the second polarizing plate each include a polarizer and a translucent protective film that sandwiches the polarizer.
When the refractive index of 550 nm in the x-axis, y-axis, and z-axis directions of the protective film is nx ₁ , ny ₁ , nz ₁ , and the thickness of the protective film is d ₁ ,
The in-plane retardation Re ₁ of the protective film is Re ₁ = (nx ₁ −ny ₁ ) d ₁ ,
When the thickness direction retardation Rth of the protective film is Rth = {(nx ₁ + ny ₁ ) / 2−nz ₁ } d ₁ ,
The in-plane retardation Re ₁ of the protective film satisfies 0 nm ≦ Re ₁ ≦ 5 nm,
The thickness direction retardation Rth of the protective film satisfies 20 nm <Rth ≦ 40 nm,
When the refractive index of 550 nm in each of the x-axis, y-axis, and z-axis directions of the retardation film is nx ₂ , ny ₂ , nz ₂ , and the thickness of the retardation film is d ₂ ,
The in-plane retardation Re ₂ of the retardation film is Re ₂ = (nx ₂ −ny ₂ ) d ₂ ,
Nz of the retardation film, Nz = a _{(nx 2 -nz 2) / (} nx 2 -ny 2),
The average refractive index Nave of the retardation film is Nave = (nx ₂ + ny ₂ + nz ₂ ) /
When 3,
The in-plane retardation Re ₂ of the retardation film satisfies 100 nm ≦ Re ₂ ≦ 150 nm,
Nz value of the retardation film satisfies 0.2 ≦ Nz ≦ 0.4,
The average refractive index Nave of the retardation film satisfies 1.4 ≦ Nave ≦ 2.0.
Liquid crystal device. A liquid crystal panel having a pair of substrates and a liquid crystal layer disposed between the pair of substrates and driven by an electric field having a component parallel to the substrates;
A first polarizing plate and a second polarizing plate arranged across the liquid crystal panel;
A retardation film disposed between the first polarizing plate and the liquid crystal panel, or between the second polarizing plate and the liquid crystal panel,
The first polarizing plate and the second polarizing plate each include a polarizer and a translucent protective film that sandwiches the polarizer.
When the refractive index of 550 nm in the x-axis, y-axis, and z-axis directions of the protective film is nx ₁ , ny ₁ , nz ₁ , and the thickness of the protective film is d ₁ ,
The in-plane retardation Re ₁ of the protective film is Re ₁ = (nx ₁ −ny ₁ ) d ₁ ,
When the thickness direction retardation Rth of the protective film is Rth = {(nx ₁ + ny ₁ ) / 2−nz ₁ } d ₁ ,
The in-plane retardation Re ₁ of the protective film satisfies 0 nm ≦ Re ₁ ≦ 5 nm,
The thickness direction retardation Rth of the protective film satisfies 40 nm <Rth ≦ 60 nm,
When the refractive index of 550 nm in each of the x-axis, y-axis, and z-axis directions of the retardation film is nx ₂ , ny ₂ , nz ₂ , and the thickness of the retardation film is d ₂ ,
The in-plane retardation Re ₂ of the retardation film is Re ₂ = (nx ₂ −ny ₂ ) d ₂ ,
Nz of the retardation film, Nz = a _{(nx 2 -nz 2) / (} nx 2 -ny 2),
When the average refractive index Nave of the retardation film is Nave = (nx ₂ + ny ₂ + nz ₂ ) / 3,
The in-plane retardation Re ₂ of the retardation film satisfies 100 nm ≦ Re ₂ ≦ 150 nm,
Nz value of the retardation film satisfies −0.1 ≦ Nz <0.2,
The average refractive index Nave of the retardation film satisfies 1.4 ≦ Nave ≦ 2.0.
Liquid crystal device. The liquid crystal device according to claim 1,
The retardation film is disposed between the liquid crystal panel and the first polarizing plate,
The slow axis of the retardation film and the absorption axis of the second polarizing plate are parallel to the alignment direction of the liquid crystal layer,
The absorption axis of the first polarizing plate is orthogonal to the alignment direction of the liquid crystal layer.
Liquid crystal device. The liquid crystal device according to claim 1,
The retardation film is disposed between the liquid crystal panel and the second polarizing plate,
The slow axis of the retardation film and the absorption axis of the first polarizing plate are parallel to the alignment direction of the liquid crystal layer,
The absorption axis of the second polarizing plate is orthogonal to the alignment direction of the liquid crystal layer.
Liquid crystal device. A liquid crystal device according to any one of claims 1 to 4,
The x-axis of the protective film is the direction in which the in-plane refractive index of the protective film is maximum,
The y-axis of the protective film is a direction parallel to the surface of the protective film and perpendicular to the x-axis of the protective film;
The z axis of the protective film is the thickness direction of the protective film,
The x axis of the retardation film is the direction in which the in-plane refractive index of the retardation film is maximized,
The y-axis of the retardation film is a direction parallel to the surface of the retardation film and perpendicular to the x-axis of the retardation film,
The z axis of the retardation film is the thickness direction of the retardation film.
Liquid crystal device. A liquid crystal device according to any one of claims 1 to 5,
The liquid crystal panel is an IPS mode liquid crystal panel.
Liquid crystal device. A liquid crystal device according to any one of claims 1 to 5,
The liquid crystal panel is an FFS mode liquid crystal panel.
Liquid crystal device.   An electronic apparatus comprising the liquid crystal device according to claim 1 in a display unit.

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