WO2009057020A1

WO2009057020A1 - Autostereoscopic display device

Info

Publication number: WO2009057020A1
Application number: PCT/IB2008/054391
Authority: WO
Inventors: Jan Van Der Horst
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2007-11-02
Filing date: 2008-10-24
Publication date: 2009-05-07

Abstract

An autostereoscopic display device (100) comprising: a display panel having a plurality of pixels (140) arranged in rows in a row direction and columns in a column direction; view directing means (130) positioned over the display panel, the view directing means comprising a plurality of view directing elements, each view directing element of the plurality of view directing elements having a longitudinal axis (135) slanted at a first angle to said column direction, each pixel of the plurality of pixels (140) having an edge aligned with the longitudinal axis (135); and a non-transmissive grid defining display areas (120) of the display panel, the non-transmissive grid comprising separating sections (114) separating neighboring display areas (120a) and (120b) in the row direction, which separating sections are oriented at a further angle to said longitudinal axis (135), and wherein each pixel (140) comprises respective parts of at least two display areas (120). In such an arrangement, there are no sections of opaque material that are oriented in parallel with the focal axis 135. This further reduces banding effects. Each pixel (140) comprises respective parts of at least two display areas (120), and includes a part of the mask arrangement. The display panel may be provided without the array of lenticular elements.

Description

Autostereoscopic display device

FIELD OF THE INVENTION

The invention relates to an autostereoscopic display device having a display panel with pixels, and an array of view directing means arranged over a the display panel.

BACKGROUND OF THE INVENTION

A known autostereoscopic display device described in WO2007/069195 A2 comprises a two dimensional liquid crystal display panel having a row and column array of pixels acting as a spatial light modulator to produce a display or an image. View directing means in the form of a sheet of elongate lenticular elements extending parallel to one another overlies the display panel and the display pixels are observed through these lenticular elements.

Each lenticular element comprises an elongate semi-cylindrical lens element overlying a group of two or more display pixels in such a way that different two-dimensional sub-images provided by the two or more display pixels are directed to different views by the lenticular element. The different views may correspond to the left or right eye of a user/viewer positioned in front of the autostereoscopic display device. In this way, all sub- images together directed by the entire array of lenticular elements provide the viewer with a single stereoscopic display or image or, if more than two views are directed, a series of successive stereoscopic images when he moves his head along the views. In the known device, the lenticular elements are slanted at an angle to the column direction of the display panel pixels to share some of the reduction of pixel resolution between the column and row direction. In this case, the column direction is the vertical direction while the row direction is the horizontal direction. The pixels are overlaid with an opaque mask for creating pixel display areas, i.e. the areas of a pixel that provide the display or image data. The pixel display areas have edges that are parallel to the lenticular elements focal axis. Therewith, problems of display light intensity variations and cross talk between views introduced by slanting are reduced. SUMMARY OF THE INVENTION

The present invention seeks to provide an improved autostereoscopic display device.

The invention is defined by the independent claims. The dependent claims define advantageous embodiments.

The invention is based on the recognition that when a viewer during the movement of his head across a display or image displayed by the known autostereoscopic display device, the light intensity variations he observes are partly due to the lenticular elements imaging parts of the display panel that do not provide the display or image. Such pats include the opaque mask.

In order to reduce the effect of imaging of dark parts of the display panel or pixel, the invention provides an autostereoscopic display device with a pixel that has two or more display areas each of which is defined by the non-transmissive grid. The display areas belonging to one pixel provide the same image information, i.e. the information of the one pixel. This yields an autostereoscopic display device in which the pixel can be advantageously aligned with the longitudinal axis of the view directing elements without having sections of the non transmissive grid, such as the separating sections also being aligned with the longitudinal axis. Therewith, banding effects in an autostereoscopic display device that uses view directing means can be reduced or even eliminated. The autostereoscopic display device thus has reduced banding and reduced crosstalk while at the same time sufficient brightness levels can be maintained.

The non-transmissive grid may comprise an opaque mask arrangement for defining display areas of the display panel. However, alternative arrangements, e.g. an arrangement in which each display area is formed by one or more light emitting diodes (LEDs) and the grid is formed by the omission of LEDs in pre-selected areas of the display panel, are equally feasible.

Preferably, the view directing means comprise an array of parallel lenticular elements positioned over the display panel, in which the longitudinal axis corresponds to the focal axis of each lenticular element. The focal axis is slanted at a first angle to said column direction and each pixel has an edge aligned with the focal axis. A lenticular array is a preferred embodiment because of its excellent light output efficiency. However, the present invention is not limited to such light directing means; other known light directing means such as light barriers having openings at regular intervals are equally feasible. For such a barrier, the longitudinal axis corresponds to the orientation of its openings. Preferably, the separating sections that separate display areas in the row direction are parallel. Even more preferably their width in the row direction is uniform. This has the advantage that they are imaged by a lenticular element in such a way that they are distributed equally in the horizontal direction over the view part formed by the pixel that is imaged.

The separating sections may be slanted at a second angle to said column direction. Such an orientation further reduces banding effects. The second angle may have a value of -arctan (x/n), wherein x is the width divided by the height of a pixel, with the width being defined as the pure horizontal width at any given height of the pixel, with n being the number of parallel sections of the opaque mask arrangement that run through a pixel. At this angle, banding is efficiently suppressed.

Moreover, this angle facilitates the use of stair-shaped column electrodes that may be placed in between the pixels such that the parallel sections cover these electrodes. The use of stair- shaped column electrodes makes the display panel suitable for use in a 2-D mode because an orthogonal pixel orientation is maintained under this angle. Preferably, this orientation of the opaque bands is combined with a slant angle of arctan 1/3 the focal axis. This combination facilitates the use of a traditional RGB pixel layout, which makes the display panel particularly suitable for use in both 2-D and 3-D modes.

In an embodiment, the autostereoscopic display device further comprises a plurality of color filters, each color filter of the plurality of color filters being aligned with a respective pixel of the plurality of pixels. In case a seamless plurality of color filters can be provided, the color filters may be perfectly aligned with the pixels of the display device. This is a preferred solution, because an autostereoscopic display device is obtained that provides an image with little artifacts. However, in case at least some neighboring color filters are separated from each other by an opaque area, such opaque areas may combine to form opaque bands that are aligned with the longitudinal axis of the view directing elements, which would introduce banding effects. This may be avoided by aligning the color filters with the pixels under an angle, such that the bands formed by the opaque gaps are no longer aligned with the longitudinal axis. Banding is thus reduced, at the expense of the introduction of some crosstalk between pixels. The crosstalk can be kept at acceptable levels by limiting the misalignment between the color filters and the pixels, i.e. by keeping the alignment angle small. In a preferred embodiment each pixel comprises a combination of parts of neighboring row display areas. This limits the amount of non-transmissive grid that is included in the pixel, which means that a pixel capable of producing good brightness levels can be obtained. Furthermore, horizontal and vertical crosstalk is limited. However, other pixel arrangements are also feasible; the pixels may be defined by combining parts of two neighboring column display areas, in which case a part of the non-transmissive grid that is aligned with the rows of the display panel is included in the pixel area. The definition of a pixel is not limited to the use of parts of only two display areas. For instance, the separating sections of the non-transmissive material that define the rows of display areas may be oriented perpendicularly to the focal axis of the lenticular elements, in which case the pixels will comprise respective parts of more than two display areas.

US patent No. 6,118,584 discloses an autostereoscopic display device having an array of lenticular elements that have a vertical longitudinal, or focal, axis. The columns of the black matrix are slanted with respect with the longitudinal axis, thus yielding non- rectangular pixels. The occurrence of continuous bands of black matrix material along the lenticular longitudinal axis is thus avoided, and banding is consequently reduced. However, as a consequence of the non-rectangular pixels making an angle with the lenticular, their content is distributed over multiple views in the horizontal direction therewith giving crosstalk between views.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows an embodiment of an autostereoscopic display device according to the invention;

Fig. 2 shows another embodiment of an autostereoscopic display device according to the invention;

Fig. 3 shows another embodiment of an autostereoscopic display device according to the invention;

Fig. 4 shows another embodiment of an autostereoscopic display device according to the invention; Figs 5 A and 5B show view visibility (Vv) as a function of viewing angel (Va) of an autostereoscopic display device according to prior art and the invention, respectively.

Figs. 6A and 6B show display brightness (Db) as a function of viewing angle (Va) for an autostereoscopic display device according to the prior art and the invention respectively. DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the invention will now be described, purely by way of example, with reference to the accompanying drawings. It should be understood that the Figs. are merely schematic and are not drawn to scale.

Fig. 1 shows a first embodiment of an autostereoscopic display device 100 of the invention. The autostereoscopic display device has a display panel 111 having an array of pixels 140, wherein pixels form rows in the horizontal direction X and columns in the vertical direction Y. Only one pixel is shown for clarity. The autostereoscopic display device has a non-transmissive grid 113 comprising non-transmissive material. In this embodiment the non-transmissive grid 113 is formed by an opaque mask arrangement overlying the display panel and thus the pixels. The opaque mask arrangement, which is sometimes referred to as a black matrix, comprises bands 112 and separating sections 114. The non-transmissive grid 113 therewith defines display areas 120. In the context of the present invention, a display area is an area of the display panel or the pixel that actually provides the image or display data. Generally a display area is capable of transmitting, or reflecting light for displaying the display or image. The bands 112 act as opaque separation between display areas 120 in the column direction while the separating sections 114 act as opaque separation between display areas in the row direction. Thus, each pixel has display or image forming display areas and non-transmissive areas part of in this case the black mask.

The autostereoscopic display device 100 further comprises view directing means to generate the spatially separated plurality of views. In Fig. 1, the view directing means are implemented by a matrix or array of parallel lenticular elements 130. Only one lenticular element is shown for reasons of clarity. The lenticular elements have a longitudinal axis, i.e. a focal axis 135 that is slanted with respect to a vertical axis Y of the display panel, i.e. the axis of the display device along which columns of pixels are aligned, to improve the resolution of the display device, as previously explained. However, the focal axis 135 may also be aligned in parallel with the vertical axis Y of the display device 100 as long as a slant angle is maintained with respect to the orientation direction of the pixel columns. Such an orientation provides an excellent viewing experience in 3-D mode, but has the drawback that a more involved arrangement of color filters is required to avoid that views have a single color. For instance, a row- wise displaced arrangement of the color filters can be used, e.g. a RGBRGB pattern in a first row followed by displaced, i.e. GBRGBR pattern in the second row and so on. It will be clear that this arrangement is less suitable for use in a 2-D viewing mode.

In accordance with the invention, the pixels of the autostereoscopic display device 100 are not defined by the display areas 120. Instead, the pixels 140 are defined by the combination of parts of different display areas. Consequently, the pixels 140 typically include a part of the non-transmissive grid such as a part of the opaque mask arrangement, i.e. at least that part of the mask arrangement that defines the separation between the display areas which form parts of the same pixel. Such parts are the separating sections 114. In Fig. 1, the total display area of pixel 140 is defined by the combination of complementary parts of two neighboring display areas 120a and 120b in a row of display areas 120. The pixels 140 have two of their sides aligned with the focal axis 135 to ensure that e.g. horizontal crosstalk between different views of the autostereoscopic display device 100 is minimized. Note that neighboring pixels provide data for different views The different views of the autostereoscopic display device 100 of this example are illustrated by the different gray scales of the pixels 140; pixels having the same gray scale belong to the same view.

Advantageously, the amount of non-transmissive material that runs in parallel with the longitudinal axis of a view directing element such as a lenticular, is minimized. In other words, neighboring pixels on either side of the longitudinal axis should preferably be placed as closely together as possible without causing interference between each others output. This may for instance be achieved by placing drive elements such as the column conductors and drive transistors under or in the parallel sections of the non-transmissive material intersecting the pixels, in stead of between the closely spaced edges of the pixels . The consequence of the pixels 140 being defined by more than one display area 120 is that the parallel sections 114 of the opaque mask arrangement no longer are aligned with the focal axis 135 of the lenticular elements 130, despite the long sides of the pixels 140 being aligned with this axis. This effectively reduces banding in the autostereoscopic display device 100. This can be understood in the following manner.

A person is watching the display device such that his focus coincides with the focal axis 135 displayed in Fig.l. When this person moves his head in a horizontal direction, e.g. by turning his head, this movement causes this focal line to shift in a horizontal direction X, i.e. the focal line moves to left or to the right of the focal axis 135. In the slanted autostereoscopic display device disclosed in WO 2007/069195 A2, this movement may cause the focal line to coincide with a band of the black matrix that runs parallel with the focal axis of the lenticular elements, and that causes excessive banding since a drop in light intensity from the display is observed in going from viewing a display area to viewing an opaque area.

However, no such abrupt intensity profile is observed for a display according to the invention since the orientation of the opaque sections 114 under an angle with the focal axis 135 in the display device of the present invention ensures that the amount of opaque material across a view and across different views as observed by a moving person remains largely constant during his movement. The displacement of the focal line away from the focal axis 135 never leads to a substantial increase or decrease of opaque material in the field of view of the person watching the display device. This is especially so if all sections are parallel and have the same width in the row or horizontal direction.

Preferably, the focal axis 135 has an angle of arctan(l/3) with the vertical axis of the display panel. The sections 114 are rotated away from the focal axis 135 such that these sections have a slant orientation of -arctan(pixel width/ pixel height)/n with respect to the focal axis 135, with the pixel width being defined as the purely horizontal width at a given height, and n being defined as the number of separating sections of the opaque material bisecting the pixel area. In Fig. 1, n = 1. The arrangement shown in Fig. 1 has some particular advantages. For instance, the column conductors 150 can form a stair, such that the resulting pixel structure is still orthogonal for use as a 2-D display without lenticular lens array. In this arrangement, the pixel capacitors and transistors of a LCD based display panel can be placed in the horizontal regions 112 of the opaque mask arrangement. The horizontal regions 112 may also be used to mask interconnections between display areas.

Thus, according to the invention, although the display areas 120 no longer correspond with the active areas of the display panel, i.e. multiple display areas form part of one pixel, it is still so that one pixel provides one part of the image with all of its display areas. Hence, the pixels as defined in the autostereoscopic display device of the invention may be controlled in a conventional way.

Alternatively, in numerous prior art and future display panels, physical pixels may be defined that comprise only one display area each. Their geometric arrangement may be such that when two or more of them are combined to provide one and the same image data point, they can give the same effect as the invention. This means, however, that the real or effective pixel, i.e. the unit providing the smallest part of an image, is defined to be the pixel according to the invention. In view thereof the noion 'pixel' in the claims should be understood to mean the rela or effective pixel. In such displays the coupling or driving of two entities each having one display area such that they form a pixel according to the invention may for example be achieved by implementing appropriate driving schemes in the prior art and future display devices.

Typically, the autostereoscopic display device 100 will comprise color filters that are aligned with the pixels 140 to provide the RGB subpixels of the device. Perfect alignment of the color filters with the pixels 140 will ensure that crosstalk between the views generated by the pixels is minimized. However, care has to be taken that no significant amount of banding is introduced. This can be avoided in a number of ways. The color filters may be seamlessly interconnected, or in case the color filters are separated by an opaque area, the color filters may be aligned with the pixels 140 under an angle. This intentional misalignment avoids that the opaque areas between the color filters in the column directions combine to form opaque bands that run parallel with the longitudinal axis 135. Such bands would introduce banding effects in the view perception of the person watching the display device 100.

The intentional misalignment of the color filters with the pixels 140 introduces crosstalk between the views. For this reason, the misalignment angle should be kept small, e.g. not exceeding 5 or 10 , such that banding is reduced at the cost of modest amounts of crosstalk only.

In Fig. 1, the pixels 140 coincide with the parts of two neighboring display areas 120 in a row. This pixel shape has the advantage that only a small amount of opaque mask material, or another type of non-transmissive material, is included in the pixel, i.e. a part of the section 114 that separates the two display areas 120. Consequently, such a pixel maintains a very good resolution, because the gap, i.e. the separating section 114, between the neighboring display areas 120 can be kept very thin, especially when this gap only has to accommodate a column electrode 150. A drawback of this pixel shape is that the location of the pixel transistors and capacitors in the horizontal gaps between the rows of pixels 140 means that some additional routing may be needed to realize the required interconnections between the various elements of the display panel.

Although it is preferable that only a single section 114 of the non-transmissive material is included in the pixels 140 of the display device of the present invention to ensure that good pixel brightness levels are maintained, it is emphasized that the pixel areas may include more than one separating section 114. An example of such a display device is given in Fig. 2, in which the pixel areas 140 comprise two sections 114 of the non-transmissive grid such as an opaque mask material. A more efficient routing can be achieved with the pixel shape shown in Fig. 3. In Fig. 3, the pixels 240 overlap with the parts of two display areas 120 in neighboring rows. Consequently, the horizontal bands 112 of the non-transmissive material dissect the pixels 240. The semiconductor elements of the pixels 240 can thus be located in the heart of the pixels, which reduces the complexity of the routing. A drawback of this pixel shape in that the pixels 240 include more opaque material than the pixels 140. This may cause some modest loss in vertical resolution compared to the pixels 140.

It should be appreciated that the shape of the pixels is not limited to the shapes shown in Figs. 1, 2 and 3. Other shapes are also feasible. For instance, the horizontal areas 112 of the mask arrangement may be slanted relative to the horizontal axis of the display panel. The pixels may include parts of more than two display areas, as shown in Fig. 2. This is for instance also the case if the sections 114 are oriented perpendicularly to the focal axis 135. The pixel shape is also not limited to quadrilateral shapes. For instance, more complex shapes may be used for instance in cases where the mapping of the required components of an active matrix display device prohibits the use of quadrilateral pixel shapes. In such a case, the pixel shape may be numerically optimized to ensure that the amount of pixels in the direction of the focal axis 135 remains constant.

Moreover, it should be appreciated that although the view directing means of the autostereoscopic display device of the present invention has been described in terms of an array of lenticular elements 130, other view directing means are equally feasible. For instance, a barrier having regularly spaced apertures may be used. In case the barrier aperture may simply be a (slanted) slit, with the slant angle of the slit defining the longitudinal axis 135. However, barriers that have more complex aperture shapes may also be used. For instance, Fig. 4 shows a barrier based autostereoscopic display device in which the barrier has rectangular shaped apertures 410, with the apertures being slanted with respect to each other. In such a device, the opaque regions are slanted with respect to the local aperture areas, with the pixel shapes coinciding with the a rectangular aperture 410.

Figs. 5A and 5B show the comparison of the view visibility (Vv) of individual views 570 as a function of the view angle (Va) in a prior art autostereoscopic display device having a slanted lenticular element array (Fig. 5A) and in the autostereoscopic display device 100 of the invention (Fig. 5B). The graphs clearly demonstrate that the autostereoscopic display device 100 exhibits a much more constant view visibility (Vv) over the viewing angle range from -20 to +20 ; compare for example the shapes of the individual views 570a with those of 570b. In addition, overlap 580b between views 570b of the device according to the invention is far less than overlap 580a between views 570a of the prior art device. Thus, crosstalk, between the different views in the autostereoscopic display device 100 is reduced.

Figs. 6 A and 6B show the comparison of the display brightness (Db) as a function of the view angle (Va) in a prior art autostereoscopic display device having a slanted lenticular element array (Fig. 6A) and in the autostereoscopic display device 100 of the present invention (Fig. 6B). Variations in the display brightness are typically caused by banding and show up as peaks and valleys within the graphs of the Fig. 6A. The graphs clearly demonstrate that the autostereoscopic display device 100 is almost insensitive to banding effects since the peaks and valleys are greatly reduced in Fig. 6B, whereas the prior art display device suffers from notice banding effects at certain view angles.

Throughout this disclosure, the term 'pixel' has been used. This term refers to independently switchable display elements, and therefore includes subpixels in a color display.

In the embodiments shown, the non-transmissive grid is incorporated as a black matrix. However, other embodiments of the invention make use of such a other non- transmissive grids; for instance, in case the display areas are formed by discrete transmissive elements such as LEDs, the grid may simply be formed by the borders between display areas, in which case no additional opaque material is required.

In the embodiments described, the display panel has the form of a liquid crystal display panel. However, other display panels can be used without departing from the invention. Thus other electronic display panels may be used such as for example light emitting diode (LED) based display panels, organic molecule based LED (OLED) display panels, cathode ray tube (CRT) based display panels or plasma display panels. In case of an LCD panel, the panel may comprise a pair of plates bordering a cavity filled with a LC material, a substrate carrying a plurality of discrete cells filled with a LC material, or other known LCD panel arrangements. Alternatively, non-electronic display panels in the form of photographs, billboards and other image carrying plates or subjects may be used. Preferably, however, the display panel is reconfigurable with respect to the image displayed, i.e. an electronic display panel. In all cases within the context of the invention, the display panel is a display panel capable of providing at least two different views either simultaneously or sequentially such that a viewer observes the stereoscopic image or display. At this point, it is emphasized that according to the present invention, a display device may include devices arranged to display a static image such as electronic billboards, electronic photos or posters and so on. However, the present invention is particularly advantageous for active display devices comprising addressable pixels, e.g. monitors and TV displays, because of the aforementioned advantages relating to the orientation of the column conductors or other semiconductor devices incorporated within an active or electronic display panel.

It will be appreciated that the view directing means may comprise more than one plurality of view directing elements. For instance, the view directing means may comprise a plurality of view directing elements for generating a plurality views when an observer moves in a horizontal direction and a further plurality of view directing elements for generating a plurality of views when the observer moves in a vertical direction. Other arrangements, i.e. in which the respective longitudinal axes of the different pluralities of viewing elements are not perpendicularly oriented with respect to each other, are also feasible.

Furthermore, the view directing means may be switchable between a first state having the view directing property and a second state not having a view directing property. In that case the first state may be combined with the multiple view providing display panel to create the autostereoscopic display while the second state may be used to display a 2D image. This may be for example achieved with a switchable lenticular element as known from for example GB2398130 or US 6069650 and their contents are incorporated by reference. These states may be obtainable sequentially in time or simultaneously. In addition, when view directing elements can be addressed individually, these states may be attained distributed over the display panel area, such as to provide two dimensional information in one part and three dimensional information in another part.

The above-mentioned modifications and embodiments illustrate rather than limit the invention, and those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that the combination of these measures cannot be used to advantage.

Claims

CLAIMS:

1. An autostereoscopic display device (100) comprising: a display panel having a plurality of pixels (140) arranged in rows in a row direction and columns in a column direction; view directing means (130) positioned over the display panel, the view directing means comprising a plurality of view directing elements, each view directing element of the plurality of view directing elements having a longitudinal axis (135) slanted at a first angle to said column direction, each pixel of the plurality of pixels (140) having an edge aligned with the longitudinal axis (135); and a non-transmissive grid defining display areas (120) of the display panel, the non-transmissive grid comprising separating sections (114) separating neighboring display areas in the row direction, which separating sections are oriented at a further angle to said longitudinal axis (135), and wherein each pixel (140) comprises respective parts of at least two display areas (120).

2. An autostereoscopic display device as claimed in claim 1, wherein the separating sections have constant width in the row direction and are parallel.

3. An autostereoscopic display device as claimed in claim 1 or 2, wherein the non-transmissive grid comprises an opaque mask arrangement (112, 114).

4. An autostereoscopic display device (100) device as claimed in any of claims 1-3, wherein the separating sections (114) are slanted with respect to said column direction.

5. An autostereoscopic display device (100) as claimed in claim 4, wherein the further angle has a value of -arctan (x/n), wherein x is the width of a pixel (140) divided by the height of a pixel (140) and wherein n is the number of separating sections running through a pixel.

6. An autostereoscopic display device (100) as claimed in any of the preceding claims, further comprising a plurality of color filters, each color filter of the plurality of color filters being aligned with a respective pixel (140) of the plurality of pixels.

7. An autostereoscopic display (100) device as claimed in claim 6, wherein at least some neighboring color filters are separated from each other by an opaque area, and wherein the color filters are aligned with the pixels (140) under an angle.

8. An autostereoscopic display device (100) as claimed in any of the preceding claims, wherein each pixel (140) comprises respective parts of neighboring display areas

(120) in a row direction.

9. An autostereoscopic display device (100) as claimed in any of the preceding claims, wherein each pixel (140) comprises respective parts of neighboring display areas (120) in a column direction.