JP2012133184A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device satisfactory in display quality.SOLUTION: The liquid crystal display device comprises: a first substrate having pixel electrodes arranged so as to correspond to pixels in a display area used to display an image, and a first vertical orientation film arranged on the surfaces of the pixel electrodes; a second substrate having counter electrodes corresponding to the pixel electrodes, and a second vertical orientation film arranged on the surfaces of the counter electrodes; a sealing material arranged outside the display area and used to stick together the first and second substrates with the first and second vertical orientation films of the first and second substrates facing each other; a liquid crystal layer in which dielectric anisotropy held between the first and second substrates over a display area and a frame-like non-display area between the display area and sealing material contains negative liquid crystal molecules. In the display area, the liquid crystal molecules are controlled in orientation by orientation restricting force applied by the first and second vertical orientation films or by electric fields between the pixel electrodes and counter electrodes. In the non-display area, they are not controlled in orientation.

Description

  Embodiments described herein relate generally to a liquid crystal display device.

  Liquid crystal display devices are utilized in various fields as display devices for OA equipment such as personal computers and televisions, taking advantage of features such as light weight, thinness, and low power consumption. In recent years, liquid crystal display devices are also used as mobile terminal devices such as mobile phones, display devices such as car navigation devices and game machines.

  In particular, a vertical aligned (vertical aligned) mode liquid crystal display device has a characteristic that a high contrast ratio can be obtained. The liquid crystal layer of such a vertical alignment mode liquid crystal display panel includes liquid crystal molecules having negative dielectric anisotropy. These liquid crystal molecules are aligned substantially perpendicular to the substrate by the alignment regulating force of the alignment film when no voltage is applied between the substrates, and with respect to the substrate when a voltage is applied between the substrates. It has the property of being oriented substantially horizontally.

  When pressure is applied to the front surface of a liquid crystal display panel by pushing the liquid crystal display panel in the vertical alignment mode with a finger or the like, the orientation of the liquid crystal molecules may be locally disturbed, leading to deterioration in display quality. There is. Various methods for solving such alignment disorder of liquid crystal molecules caused by finger pressing have been proposed.

JP 2010-128248 A JP 2007-240603 A JP 2007-133304 A

  An object of the present embodiment is to provide a liquid crystal display device with good display quality.

According to this embodiment,
A first substrate provided with a pixel electrode arranged corresponding to each pixel of a display area for displaying an image and a first vertical alignment film arranged on the surface of the pixel electrode, and an opposing surface facing each of the pixel electrodes A second substrate provided with a second vertical alignment film disposed on the surface of the electrode and the counter electrode; and disposed outside the display area, wherein the first vertical alignment film of the first substrate and the second substrate A sealing material for bonding the first substrate and the second substrate with the second vertical alignment film facing each other; the display area; and a frame-like non-display area between the display area and the sealing material A liquid crystal layer including a liquid crystal molecule having a negative dielectric anisotropy held between the first substrate and the second substrate, and the liquid crystal molecule of the liquid crystal layer includes the display area. In the first vertical alignment film and the second vertical alignment film. Oriented controlled by an electric field between the counter electrode and an alignment regulating force or the pixel electrode by film, the in the non-display area, the liquid crystal display device is provided, characterized in that not oriented control.

FIG. 1 is a plan view schematically showing the configuration of the liquid crystal display device according to the present embodiment. FIG. 2 is a cross-sectional view schematically showing an example of the structure of the liquid crystal display panel shown in FIG. FIG. 3 is a conceptual diagram showing a cross section of the liquid crystal layer in the white display state in the liquid crystal display panel of the first configuration example. FIG. 4 is a cross-sectional view schematically showing another example of the structure of the liquid crystal display panel shown in FIG. FIG. 5 is a conceptual diagram showing a cross section of the liquid crystal layer in the white display state in the liquid crystal display panel of the second configuration example.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. In each figure, the same reference numerals are given to components that exhibit the same or similar functions, and duplicate descriptions are omitted.

  FIG. 1 is a plan view schematically showing a configuration of a liquid crystal display device 1 in the present embodiment.

  That is, the liquid crystal display device 1 includes an active matrix type liquid crystal display panel LPN, a drive IC chip 2 connected to the liquid crystal display panel LPN, a flexible wiring board 3, and the like.

  The liquid crystal display panel LPN includes a display area (sometimes referred to as an active area) ACT for displaying an image. This display area ACT is formed of, for example, a plurality of pixels PX formed in a substantially rectangular shape and arranged in an m × n matrix (where m and n are positive integers).

  Such a liquid crystal display panel LPN includes an array substrate AR as a first substrate, a counter substrate CT as a second substrate disposed so as to face the array substrate AR, and the array substrate AR and the counter substrate CT. And a liquid crystal layer LQ held therebetween.

  The array substrate AR includes a gate line GL extending along the first direction X, a source line SL extending along the second direction Y orthogonal to the first direction X, and the like. The array substrate AR is connected to the gate line GL and the source line SL, and is arranged corresponding to each pixel PX. The pixel electrode is connected to the switching element SW and arranged corresponding to each pixel PX. PE etc. are provided. The counter substrate CT includes a counter electrode CE that faces each of the pixel electrodes PE through the liquid crystal layer LQ.

  The seal material SE is disposed outside the display area ACT, and bonds the array substrate AR and the counter substrate CT together. In the illustrated example, the sealing material SE is formed in a substantially rectangular frame shape and is formed in a closed loop shape that does not have an injection port for injecting a liquid crystal material. However, the sealing material SE is not limited to this example. An injection port may be formed. When the injection port is formed, after the liquid crystal material is injected from the injection port, the injection port is sealed with a sealing material such as an ultraviolet curable resin.

  A frame-like non-display area NDP is formed between the display area ACT and the sealing material SE. In the non-display area NDP, a light shielding layer SH is disposed. Such a light shielding layer SH may be formed on any surface of the array substrate AR, or may be formed on any surface of the counter substrate CT.

  FIG. 2 is a cross-sectional view schematically showing an example of the structure of the liquid crystal display panel LPN shown in FIG.

  The array substrate AR is formed by using a first insulating substrate SUB1 having optical transparency such as a glass substrate or a plastic substrate. The array substrate AR includes a switching element SW, a pixel electrode PE, a first vertical alignment film AL1, and the like on the side of the first insulating substrate SUB1 facing the counter substrate CT. The switching element SW and the pixel electrode PE are arranged corresponding to each pixel PX in the display area ACT.

  The switching element SW is configured by a thin film transistor (TFT) or the like. The switching element SW may be a top gate type or a bottom gate type, and includes a semiconductor layer formed of polysilicon, amorphous silicon, or the like, although not described in detail.

  The pixel electrode PE is electrically connected to the switching element SW. The pixel electrode PE is formed of a light-transmitting conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO).

  The first vertical alignment film AL1 is disposed on the surface of the array substrate AR that faces the counter substrate CT, and extends over substantially the entire display area ACT. That is, the first vertical alignment film AL1 is disposed on the surface of the pixel electrode PE of each pixel PX.

  On the other hand, the counter substrate CT is formed using a second insulating substrate SUB2 having optical transparency such as a glass substrate or a plastic substrate. The counter substrate CT includes a counter electrode CE, a second vertical alignment film AL2, and the like on the side of the second insulating substrate SUB2 facing the array substrate AR. Although not shown in the figure, this counter substrate CT alleviates the influence of the black matrix partitioning each pixel PX, the color filter layer arranged corresponding to each pixel PX, and the unevenness of the surface of the color filter layer. An overcoat layer or the like may be disposed.

  The counter electrode CE is opposed to each pixel electrode PE of each pixel PX. The counter electrode CE extends over substantially the entire display area ACT, and is disposed in common for each pixel PX. Such a counter electrode CE is formed of a light-transmitting conductive material such as ITO or IZO, for example.

  The second vertical alignment film AL2 is disposed on the surface of the counter substrate CT facing the array substrate AR, and extends over substantially the entire display area ACT. That is, the second vertical alignment film AL2 is disposed on the surface of the counter electrode CE.

  The first vertical alignment film AL1 and the second vertical alignment film AL2 do not require an alignment processing step typified by rubbing, and a state in which no potential difference is formed between the pixel electrode PE and the counter electrode CE, that is, When no electric field is formed between the pixel electrode PE and the counter electrode CE, the liquid crystal molecules LM of the liquid crystal layer LQ are respectively transferred to the main surface of the first insulating substrate SUB1 (or the array substrate AR) and the second insulating substrate. It has a characteristic of being oriented substantially perpendicular to the main surface of SUB2 (or counter substrate CT).

  The array substrate AR and the counter substrate CT as described above are arranged so that the first vertical alignment film AL1 and the second vertical alignment film AL2 face each other. At this time, between the first vertical alignment film AL1 of the array substrate AR and the second vertical alignment film AL2 of the counter substrate CT, a spacer (for example, a columnar shape formed integrally with one substrate by a resin material). A predetermined cell gap is formed by the spacer.

  The sealing material SE is disposed outside the display area ACT. The sealing material SE bonds the array substrate AR and the counter substrate CT together with the first vertical alignment film AL1 and the second vertical alignment film AL2 facing each other. Such a sealing material SE is formed of, for example, an ultraviolet curable resin or a thermosetting resin.

  The liquid crystal layer LQ is held in a cell gap formed between the array substrate AR and the counter substrate CT over the inner side surrounded by the sealing material SE, that is, over the display area ACT and the non-display area NDP. The liquid crystal layer LQ includes liquid crystal molecules LM having a negative dielectric anisotropy.

  The light shielding layer SH is disposed in the non-display area NDP between the display area ACT and the seal material SE. In the illustrated example, the light shielding layer SH is formed on a surface of the counter substrate CT facing the array substrate AR. Such a light shielding layer SH is formed using, for example, a light shielding metal or a black resin.

  A first optical element OD1 having a first polarizing plate PL1 is disposed on one outer surface of the liquid crystal display panel LPN, that is, on the outer surface of the first insulating substrate SUB1 constituting the array substrate AR. A second optical element OD2 having a second polarizing plate PL2 is disposed on the other outer surface of the liquid crystal display panel LPN, that is, the outer surface of the second insulating substrate SUB2 constituting the counter substrate CT. For example, the first polarizing plate PL1 and the second polarizing plate PL2 are arranged so that their absorption axes are orthogonal to each other.

  In such a vertical alignment (VA) mode liquid crystal display device, the liquid crystal molecules LM are aligned substantially perpendicularly to the substrate when no electric field is formed between the pixel electrode PE and the counter electrode CE. . At this time, of the light from the backlight (not shown) arranged on the back side of the liquid crystal display panel LPN, the linearly polarized light transmitted through the first polarizing plate PL1 is absorbed by the second polarizing plate PL2. For this reason, the liquid crystal display device is in a black display state. Further, in a state where an electric field is formed between the pixel electrode PE and the counter electrode CE, the liquid crystal molecules LM are aligned substantially parallel (that is, horizontally) to the substrate. At this time, of the light from the backlight, the linearly polarized light that has passed through the first polarizing plate PL1 passes through the second polarizing plate PL2. For this reason, the liquid crystal display device is in a white display state. Thereby, a normally black mode is realized.

  In the present embodiment, in the display area ACT, the liquid crystal molecules LM of the liquid crystal layer LQ are aligned by the first vertical alignment film AL1 and the second vertical alignment film AL2, or the electric field between the pixel electrode PE and the counter electrode CE. In the non-display area NDP, the orientation is not controlled.

  A specific configuration example will be described below.

  In the first configuration example shown in FIG. 2, the first vertical alignment film AL1 and the second vertical alignment film AL2 that impart alignment regulating force to the liquid crystal molecules LM extend over the display area ACT. On the other hand, it is not arranged in the non-display area NDP. That is, the first vertical alignment film AL1 and the second vertical alignment film AL2 are missing between the display area ACT and the seal material SE.

  More specifically, the first vertical alignment film AL1 covers up to the pixel electrode PE (E) of the outermost peripheral pixel PX (E) located at the outermost periphery of the display area ACT, but is opposed to the light shielding layer SH. Does not extend to position. The second vertical alignment film AL2 covers up to the counter electrode CE facing the pixel electrode PE (E), but does not extend on the light shielding layer SH.

  In the illustrated example, the non-display area NDP is formed across the width of three pixels. In the array substrate AR, the pixel electrodes PE and the switching elements SW are not arranged in the non-display area NDP, but dummy pixel electrodes and switching elements that do not contribute to display may be arranged. In the counter substrate CT, the counter electrode CE is not arranged in the non-display area NDP, but may extend from the display area ACT. In the configuration in which the power feeding unit that supplies a potential to the counter electrode CE from the array substrate side is disposed outside the sealing material SE, the non-display area is used to electrically connect the power feeding unit and the counter electrode CE. The counter electrode CE may be disposed on a part of the NDP.

  FIG. 3 is a conceptual diagram showing a cross section of the liquid crystal layer LQ in the white display state (state in which an electric field is formed between the pixel electrode and the counter electrode) in the liquid crystal display panel LPN of the first configuration example. In FIG. 3, only the configuration necessary for the description is shown.

  That is, in the display area ACT, the liquid crystal molecules LM of the liquid crystal layer LQ are aligned substantially parallel to the substrate. On the other hand, in the non-display area NDP between the display area ACT and the sealing material SE, the alignment of the liquid crystal molecules LM is not uniform, and a fine alignment disorder (defect) occurs. This is because the liquid crystal molecules LM in the non-display area NDP are not affected by the alignment regulating force by the first vertical alignment film AL1 and the second vertical alignment film AL2, and the alignment control is not performed by the electric field between the pixel electrode and the counter electrode. Because it is not done. For this reason, the liquid crystal molecules LM in the non-display area NDP try to align in a direction perpendicular to the substrate, but are not uniformly aligned.

  As described above, when the liquid crystal molecules LM in the display area ACT are aligned in parallel with the substrate for white display or the like, they are pressed on the front surface of the liquid crystal display panel LPN (that is, the counter substrate CT) by pressing with a finger. When pressure is applied at a point or surface, stress and orientation distortion due to deformation of the liquid crystal display panel LPN are gradually and quickly propagated to the peripheral portion of the outer periphery of the liquid crystal display panel LPN at and near the pressed position. The alignment order of the liquid crystal molecules LM is maintained.

  The stress and orientation strain propagated from the display area ACT are relaxed, absorbed, or dispersed in minute defects in the liquid crystal layer LQ in the non-display area NDP. For this reason, it becomes possible to suppress the re-propagation of the stress reaching the non-display area NDP and the strain of orientation to the display area ACT.

  Therefore, according to the first configuration example, it is possible to provide a liquid crystal display device with improved display quality by improving display defects in the peripheral portion of the liquid crystal display panel LPN caused by finger pressing or the like.

  Further, since the non-display area NDP is shielded from light by the light shielding layer SH and does not contribute to the display, for example, the orientation of the liquid crystal molecules LM is disturbed due to the stress propagated from the display area ACT or the orientation distortion, and the cell gap Even if non-uniformity occurs, the display quality is hardly affected.

  In the first configuration example, the first vertical alignment film AL1 and the second vertical alignment film AL2 are disposed in the display area ACT, while the first vertical alignment film AL1 and the second vertical alignment film AL2 are disposed in the non-display area NDP. The region having the alignment state different from that of the display area ACT is formed in the periphery of the display area ACT, but the region subjected to the alignment process different from that of the display area ACT is formed in the periphery of the display area ACT. The display area NDP may be used.

  FIG. 4 is a cross-sectional view schematically showing another example of the structure of the liquid crystal display panel LPN shown in FIG.

  In the second configuration example shown in FIG. 4, the pixel electrode PE capable of forming an electric field with the counter electrode CE is not arranged in the non-display area NDP. In the illustrated example, the non-display area NDP is formed across the width of three pixels. The first vertical alignment film AL1 and the second vertical alignment film AL2 are arranged from the display area ACT to the non-display area NDP.

  FIG. 5 is a conceptual diagram showing a cross section of the liquid crystal layer LQ in the white display state (state in which an electric field is formed between the pixel electrode and the counter electrode) in the liquid crystal display panel LPN of the second configuration example. In FIG. 5, only the configuration necessary for the description is shown.

  That is, in the display area ACT, the liquid crystal molecules LM of the liquid crystal layer LQ are aligned substantially parallel to the substrate. On the other hand, in the non-display area NDP, the liquid crystal molecules LM are aligned substantially perpendicular to the substrate under the influence of the alignment regulating force by the first vertical alignment film AL1 and the second vertical alignment film AL2. However, the alignment of the liquid crystal molecules LM in the non-display area NDP is not controlled by the electric field between the pixel electrode and the counter electrode.

  As described above, when the liquid crystal molecules LM in the display area ACT are aligned in parallel with the substrate for white display or the like, pressure is applied to the front surface of the liquid crystal display panel LPN by a point or a surface by pressing with a finger or the like. In this case, the stress and orientation strain transmitted from the display area ACT propagate to the non-display area NDP. At this time, the alignment disorder of the liquid crystal molecules LM occurs in the non-display area NDP. However, in this non-display area NDP, the alignment state of the liquid crystal molecules LM is different from the display area ACT, and therefore the propagation speed of the alignment disorder is shifted. As a result, it is possible to suppress repropagation of the disorder of orientation to the display area ACT.

  Therefore, also in such a second configuration example, a display defect in the peripheral portion of the liquid crystal display panel LPN caused by finger pressing or the like can be improved, and a liquid crystal display device with good display quality can be provided.

  In the present embodiment, in the vertical alignment mode liquid crystal display panel LPN, as long as a region having an alignment state different from that of the display area ACT is formed in the periphery of the display area ACT, The configuration is not limited to two. For example, in the non-display area NDP, at least one of the surface of the array substrate AR facing the counter substrate CT and the surface of the counter substrate CT facing the array substrate AR does not affect the orientation of the display area ACT. Fine protrusions for disturbing the orientation may be provided. Such minute protrusions can be formed using a resin material for forming a spacer, a black matrix, a color filter layer, an overcoat layer, or the like, or a conductive material for forming various electrodes or wirings.

(Comparative example)
A liquid crystal display panel LPN was prepared in which the non-display area NDP was not provided and the sealing material SE was disposed on the outer periphery of the display area ACT. With respect to the liquid crystal display panel LPN of such a comparative example, when the liquid crystal molecules LM are aligned in parallel with the substrate for white display or the like, a dot or surface is formed on the front surface of the liquid crystal display panel LPN by pressing with a finger or the like. Pressure was applied. At this time, the orientation of the liquid crystal molecules LM is locally disturbed in the region where the pressure is propagated, mainly in the periphery of the liquid crystal display panel LPN, and the orientation state in which the liquid crystal molecules LM are oblique or nearly perpendicular to the substrate is formed. . Such an alignment state changes depending on the pressure intensity and the elapsed time, and is essentially the same as the alignment state in a halftone display or a black display, so that a black display is displayed in the peripheral portion of the liquid crystal display panel LPN despite the white display. Display defects such as unevenness and ripples occurred.

  At this time, the reason why the display defect occurred slightly inside rather than the outermost peripheral portion closest to the seal material SE is that the panel is more easily deformed than the outermost peripheral portion fixed firmly by the seal material SE or the like, The deterioration of the degree of display failure as the glass plate thickness of the panel is reduced is considered to be due to an increased amount of deformation during pressing.

  On the other hand, according to the present embodiment, with respect to the structure of the comparative example, the liquid crystal molecules LM having the alignment state and behavior different from those of the display area ACT are filled outside the display area ACT and inside the sealant SE. A display area NDP is provided. In this non-display area NDP, the strain of orientation generated in the liquid crystal display panel LPN is relaxed, absorbed and dispersed, so that the influence on the display quality can be reduced even if stress or deformation of the liquid crystal display panel LPN is applied. .

  In the present embodiment, it is desirable that the width of the non-display area NDP corresponds to a length of 3 pixels or more. According to various studies made by the inventor, particularly where a display defect occurs in a small liquid crystal display panel LPN having a rectangular display area ACT with a diagonal size of 2.5 to 3.0 type. Further, it has been found that display defects are likely to occur in a region including the outermost peripheral pixel PX (E) in the display area ACT and a total of three pixels corresponding to two pixels inward from the outermost peripheral pixel PX (E). Therefore, it is desirable that the non-display area NDP is formed over at least three pixels. However, when a narrow frame is required, it is desirable not to make the width of the non-display area NDP excessively long.

  In the present embodiment, a configuration in which a touch panel is disposed on the front surface of the liquid crystal display panel LPN is also applicable. In such a configuration, it is possible to suppress the occurrence of display defects in the periphery of the display area ACT due to touching the touch panel.

  As described above, according to this embodiment, it is possible to provide a liquid crystal display device with good display quality.

  In addition, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device LPN ... Liquid crystal display panel AR ... Array substrate CT ... Opposite substrate LQ ... Liquid crystal layer LM ... Liquid crystal molecule SE ... Sealing material ACT ... Display area PX ... Pixel PX (E) ... Outermost pixel SW ... Switching element PE ... Pixel electrode CE ... Counter electrode AL1 ... First vertical alignment film AL2 ... Second vertical alignment film NDP ... Non-display area SH ... Light shielding layer

Claims (5)

A first substrate including a pixel electrode disposed corresponding to each pixel of a display area for displaying an image, and a first vertical alignment film disposed on a surface of the pixel electrode;
A second substrate including a counter electrode facing each of the pixel electrodes and a second vertical alignment film disposed on a surface of the counter electrode;
The first substrate and the second substrate are pasted with the first vertical alignment film of the first substrate and the second vertical alignment film of the second substrate facing each other disposed outside the display area. Sealing material to match,
Liquid crystal molecules having a negative dielectric anisotropy held between the first substrate and the second substrate over the display area and a frame-like non-display area between the display area and the sealing material A liquid crystal layer containing,
The liquid crystal molecules of the liquid crystal layer are aligned in the display area by an alignment regulating force by the first vertical alignment film and the second vertical alignment film or an electric field between the pixel electrode and the counter electrode, The liquid crystal display device is characterized in that the alignment is not controlled in the non-display area.   The liquid crystal display device according to claim 1, wherein the first vertical alignment film and the second vertical alignment film extend over the display area and are not arranged in the non-display area.   The liquid crystal display device according to claim 1, wherein the pixel electrode capable of forming an electric field with the counter electrode is not disposed in the non-display area.   The liquid crystal display device according to any one of claims 1 to 3, further comprising a light shielding layer disposed in the non-display area.   4. The liquid crystal display device according to claim 1, wherein the width of the non-display area corresponds to a length of three pixels or more.

Images