JP2006003754A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device which controls a visual field angle. <P>SOLUTION: In the display device, a visual field angle controller 120 and a display element 110 are arranged so that respective display surfaces are overlapped with each other. In the visual field angle controller 120, portions, in which changes in transmissivity and/or color are made by electric signals from the external so that characters are visually recognized along a prescribed visual field angle, are provided. Along a main visual field angle direction, no character is visually recognized and display on the display element is visually recognized. Furthermore, along a prescribed visual field angle direction, the characters of the visual field angle controller 120 and display of the display element 110 are seen in an overlapped manner. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a display device capable of controlling a viewing angle.

  Currently, display devices are widely used as an interface for connecting people and machines, and have made remarkable progress. In many cases, it is preferable that the viewing angle of the display device is wide. Therefore, the development of display devices has been advanced in the direction of widening the viewing angle.

  Information with high security may be displayed on such a display device. At this time, if information with high security is displayed on a display device with a wide viewing angle, the display may be viewed by a third party. Therefore, it is not necessarily preferable that the viewing angle of the display device is wide. Therefore, the need to control the viewing angle within a specific range is increasing due to the demand for privacy protection.

Various means have been developed as a viewing angle control technique for display devices (see, for example, Patent Documents 1 to 3 and Non-Patent Document 1).
Japanese Patent Laid-Open No. 11-84357 Japanese Patent Laid-Open No. 8-114795 JP 2001-264768 A Shoichi Matsumoto and Ryo Kakuda, “Basics and Applications of Liquid Crystals”, Industrial Research Committee, May 20, 1991, Chapter 10 9.2

  As a conventional viewing angle control technique, for example, a method using a louver is known. However, since the viewing angle is always fixed, there is a problem that it cannot be eliminated even when viewing angle control is not required. Therefore, it is difficult to apply this method.

  Also, a method using a viewing angle control plate whose transmission / scattering characteristics change depending on the viewing angle has been proposed. However, this method has a problem that it is troublesome to attach / detach the viewing angle control plate to / from the display device. Also, when the viewing angle control plate is always fixedly arranged, it cannot be switched, so that it is not possible to meet the demand for easily switching between the wide viewing angle characteristic and the narrow viewing angle characteristic according to the user's application. Furthermore, the method using such a viewing angle control plate has a problem that the transmittance in the front direction falls.

  A technique for constructing a viewing angle control device using a liquid crystal display element has also been proposed. In this technique, the viewing angle of the liquid crystal display is configured to be different by changing the alignment direction of the liquid crystal to a plurality of directions. Then, using such a special orientation state, a fixed pattern is displayed. Specifically, as shown in the partial diagram (A) of FIG. 7, when the character pattern 1 is displayed on the display element, the checkered fixed pattern 2 as shown in the partial diagram (B) is viewed. Display on the angle controller. Then, when viewed from an oblique direction, the display of the character pattern 1 and the fixed pattern 2 is overlapped and looks like a partial diagram (C). However, in such a conventional technique, since a human can identify only a character portion, there is a possibility that information (character pattern) displayed on the display element may be visually recognized even from a direction other than the main viewing angle. .

  One of the objects of the present invention is to obtain a wide viewing angle characteristic without deteriorating the display characteristic in the front direction, and a display capable of arbitrarily and easily switching a viewing angle characteristic that is difficult to view from a wide viewing angle. Is to provide a device.

  A first aspect of the present invention is a display device in which a viewing angle control device and a display element are arranged so that their display surfaces overlap each other. The viewing angle control device includes characters in a specific viewing angle direction. Is provided with a portion whose transmittance and / or color can be changed by an electrical signal from the outside, from the main viewing angle direction, the characters are not visually recognized, and the display of the display element is visually recognized, Provided is a display device configured so that a display of a display element and the character appear to overlap each other in a specific viewing angle direction. As a result, it is possible to switch between a state in which a wide viewing angle is obtained and a state in which a narrow viewing angle is obtained, and deterioration of display characteristics in the front direction can be prevented.

  A 2nd aspect provides the display apparatus of the aspect 1 in which the said character comprises the sentence which has a meaning. This makes it more difficult to view the display screen from a direction other than the front in a state where a narrow viewing angle is obtained.

  A third aspect provides the display device according to aspect 1 or 2, wherein the character is hiragana. This makes it more difficult to view the display screen from a direction other than the front in a state where a narrow viewing angle is obtained.

  A 4th aspect provides the display apparatus of the aspect 1, 2 or 3 which is 1/2 to 2 times the size of the character which the said character appears in the display of a display element. This makes it more difficult to view the display screen from a direction other than the front in a state where a narrow viewing angle is obtained.

  According to a fifth aspect, there is provided the display device according to any one of the first, second, and third aspects, wherein the character is substantially equal to a size of a character appearing on a display element. This makes it more difficult to view the display screen from a direction other than the front in a state where a narrow viewing angle is obtained.

  In a sixth aspect, the display device according to any one of the first, second, third, fourth, or fifth aspect is presented by using a difference in optical effect depending on a viewing angle direction of an optical substance provided in the viewing angle control device. provide.

  According to a seventh aspect, there is provided the display device according to any one of the first to sixth aspects, wherein the optical material showing the birefringence of the character is formed by controlling the orientation corresponding to the shape of the character. .

  In an eighth aspect, the viewing angle control device is a liquid crystal display element in which a liquid crystal layer is sandwiched between a pair of electrodes-attached substrates, the liquid crystal of the liquid crystal layer is in parallel alignment, and Δn · d of the liquid crystal layer is 1 The display apparatus in any one of the aspects 1-7 which are 0.0 micrometer or more is provided.

A ninth aspect provides the display device according to aspect 8, wherein the viewing angle control device is provided with a polarizing layer having a transmission axis parallel or perpendicular to the alignment direction of the liquid crystal.
In addition, in said aspect, it is preferable that the sentence which has a meaning is a well-known thing, such as a classic and modern literature.

  According to the present invention, it is possible to obtain a wide viewing angle characteristic without deteriorating the display characteristic in the front direction, and arbitrarily and easily switch from the wide viewing angle characteristic state to the viewing angle characteristic state that is difficult to view. it can.

  Hereinafter, the present invention will be described with reference to the drawings. In addition, these figures and description illustrate this invention, and do not restrict | limit the scope of the present invention. Further, it goes without saying that other forms may also belong to the category of the present invention as long as they are consistent with the present invention.

FIG. 1 is a schematic cross-sectional view of a display device 100 according to the present invention. A liquid crystal display device will be described as an example of the display element 110.
The display device 100 includes a viewing angle control device 120 and a display element 110. The display element 110 is a liquid crystal display device that includes a liquid crystal display element 112 and a backlight unit 111. Assuming that the upper side of the drawing is the viewing side, the liquid crystal display element 112 is provided on the viewing side of the backlight unit 111, and the viewing angle control device 120 is provided on the viewing side of the liquid crystal display element 112.

  As the backlight unit 111, a known unit including a fluorescent tube (not shown) and a light guide plate (not shown) can be used.

  The liquid crystal display element 112 may be a conventionally known TN type or STN type passive matrix driving type or an active matrix driving type using TFTs. Further, a polarizing layer having a transmission axis arranged in a predetermined direction is provided on the viewing side and the non-viewing side of the liquid crystal display element 112 according to the alignment direction.

  FIG. 1 shows an example in which the viewing angle control device 120 is arranged on the viewing side of the liquid crystal display element 112. Further, the viewing angle control device 120 may be disposed between the backlight unit 111 and the liquid crystal display element 112.

The configuration of the viewing angle control device 120 will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view of the viewing angle control device 120.
The first substrate 121a and the second substrate 121b may be, for example, a transparent glass substrate or a resin substrate, or a combination of a glass substrate and a resin substrate.

  In the case of a resin substrate, a resin substrate with an electrode that is continuously supplied is sandwiched between two rubber rolls, and a liquid crystal containing and dispersed spacers is supplied between the two, and then sealed to form a liquid crystal display element. High productivity is possible.

  In the case of a glass substrate, a small amount of spacers are scattered on the electrode forming surface, the four sides of the glass substrate facing each other are sealed with a sealing agent such as epoxy resin, and one of the cutouts of the seals provided at two or more locations is liquid crystal The cell is filled with liquid crystal by being dipped in and sucked from the other, and a liquid crystal display element can be obtained. A vacuum injection method can also be used.

  Patterns of the first electrode 122a and the second electrode 122b are formed on the first substrate 121a and the second substrate 121b, respectively. The first electrode 122a and the second electrode 122b are formed of a transparent conductive film such as ITO. The first electrode 122a and the second electrode 122b are patterned corresponding to the display screen. This display pattern will be described in detail later.

  A first alignment film 123a and a second alignment film 123b for aligning liquid crystals are provided on the first electrode 122a and the second electrode 122b, respectively. The first alignment film 123a and the second alignment film 123b are formed by, for example, printing an organic film such as polyimide on the substrate surface and performing alignment treatment (rubbing treatment) on the alignment film surface. It is formed by forming a film.

  The distance between the first substrate 121a and the second substrate 121b is held by a spacer (not shown). The spacers (not shown) are made of acrylic resin or the like and are spread on the first substrate 121a. A columnar spacer may also be used.

  The surface of the first substrate 121a on which the electrode 122a and the alignment film 123a are provided and the surface of the second substrate 121b on which the electrode 122b and the alignment film 123b are provided are arranged to face each other. At this time, the alignment films 123 a and 123 b are arranged so that the alignment directions are parallel to each other, and are bonded using the sealing material 124. The sealing material 124 is made of, for example, epoxy resin, and is applied in a predetermined pattern on the first substrate 121a or the second substrate 121b.

  Liquid crystal is injected between the substrates thus bonded to form a liquid crystal layer 125. As the liquid crystal material, known nematic liquid crystal can be used. The liquid crystal layer 125 is parallel aligned along the alignment direction of the alignment films 123a and 123b. After injecting liquid crystal, sealing is performed using a sealant.

  A polarizing layer 126 is provided outside the substrate. Here, in the viewing angle control device 120 shown in FIG. 1, an example is shown in which a polarizing layer is arranged on the viewing side and no polarizing layer is provided on the non-viewing side (see FIG. 2). Usually, a polarizing layer is provided on each of the viewing side and the non-viewing side of the liquid crystal display element 112. Therefore, the light emitted from the liquid crystal display element 112 is linearly polarized light. When the viewing angle control device 120 is disposed on the viewing side of the liquid crystal display element 112, it is not necessary to provide a polarizing layer on the non-viewing side of the viewing angle control device 120, and only the polarizing layer 126 is provided on the viewing side. Good. According to such a configuration, since no polarizing layer is provided on the liquid crystal display element 112 side of the viewing angle control device 120, it is possible to prevent a decrease in luminance due to light absorption by the polarizing layer.

  When the viewing angle control device 120 is disposed between the backlight unit 111 and the liquid crystal display element 112, a polarizing layer is provided on the non-viewing side of the viewing angle control device 120, and a polarizing layer is provided on the viewing side. Absent. In addition, if the light emitted from the backlight unit 111 has a polarization property, the polarizing layer on the non-viewing side of the viewing angle control device 120 may not be provided. Thereby, the brightness | luminance fall by a polarizing layer can be prevented further.

  As the polarizing layer 126, a polarizing plate produced by stretching generally known polyvinyl alcohol or the like is used. In order to further increase the luminance, a reflective polarizing plate or the like may be used as the polarizing layer 126.

The direction of the transmission axis of the polarizing layer 126 will be described with reference to FIG.
In FIG. 3, an exploded perspective view of the viewing angle control device 120 is shown together with the liquid crystal display element 112. The liquid crystal layer 125 of the viewing angle control device 120 shown in FIG. 3 is not in a state where a voltage is applied. In FIG. 3, the arrow indicates the direction of the transmission axis. That is, light that vibrates in a direction parallel to the arrow passes through the viewing angle control device 120. The transmission axis of the liquid crystal display element 112 is arranged in parallel to the alignment direction of the liquid crystal layer 125 of the viewing angle control device 120. In this state, the light incident from the liquid crystal display element 112 is transmitted through the liquid crystal layer 125 of the viewing angle control device 120 without causing a phase difference from any direction. The transmission axis of the polarizing layer 126 is arranged in parallel with the alignment direction of the liquid crystal layer 125. In this state, the light transmitted through the liquid crystal layer 125 passes through the polarizing layer 126 as it is and exits to the viewer side. Alternatively, the transmission axis of the liquid crystal display element 112 and the alignment direction of the liquid crystal layer 125 may be arranged at a right angle. In this case, the transmission axis of the polarizing layer 126 is perpendicular to the alignment direction of the liquid crystal layer 125.

Here, the operation of the viewing angle control device 120 will be described. In the following description, when a liquid crystal cell is used in the viewing angle control device 120, the viewing angle control device 120 is referred to as a viewing angle control cell.
The light emitted from the backlight unit 111 passes through the liquid crystal display element 112 and becomes linearly polarized light by the polarizing layer disposed on the viewing side of the liquid crystal display element 112. When no voltage is applied between the electrodes 122a and 122b of the viewing angle control device 120, the liquid crystal layer 125 is oriented in the same direction as the incident linearly polarized light. Therefore, when viewed from the front, the birefringence effect is not generated on the incident light, and the light passes through the liquid crystal layer 125 as it is. Although the phase difference occurs as the viewing angle is widened, by optimizing the refractive index anisotropy Δn and the cell gap d, display can be performed without much difference from the display characteristics of the conventional liquid crystal display element 112. The direction of the transmission axis of the polarizing layer 126 disposed on the viewing side of the viewing angle control device 120 is the same as the linearly polarized light that has passed through the viewing angle control device 120. To Penetrate.

  When a voltage is applied between the opposing electrodes 122a and 122b of the viewing angle control device 120, the liquid crystal molecules in the liquid crystal layer 125 change direction in the same direction as the electric field. That is, the liquid crystal molecules have a positive dielectric anisotropy and change the alignment direction perpendicular to the two substrates. At this time, incident light is transmitted without generating birefringence in the direction perpendicular to the main surface (display surface) of the substrate, but birefringence occurs in the oblique direction, and the transmittance changes. Also, since the optical path length varies depending on the viewing angle, it looks colored.

  When displaying using the birefringence effect of the liquid crystal, the contrast is lowered. In the viewing angle control device 120 of the present invention using this, the viewing angle control effect is small as it is. Therefore, in the present invention, the electrode 122 of the viewing angle control device 120 is patterned so as to be a continuous sentence of hiragana. The human eye has a function of recognizing characters by interpolating a portion between displays when reading the characters. In consideration of this, displaying the same message according to the character displayed on the liquid crystal display element 112 can hinder the visual recognition of the display message.

  Further, when the angle from the normal direction of the main surface (display surface) of the display device 100, that is, the viewing angle θ is increased, the influence of the pattern of the viewing angle control device 120 becomes stronger. When the display device 100 is viewed from an angle greater than a certain angle, the display on the liquid crystal display element 112 cannot be visually recognized (see FIG. 1).

  4, 5, and 6 show examples of images that are displayed and viewed on the liquid crystal display element 112, the viewing angle control device 120, and the display device 100. A partial diagram (A) is an image displayed on the liquid crystal display element 112 and visually recognized, and a partial diagram (B) is displayed on the viewing angle control device 120 and is displayed when viewed from an oblique direction. Indicates a display that is visually recognized when the display device 100 is viewed obliquely in a state where a viewing angle characteristic that is difficult to visually recognize from a wide viewing angle is obtained.

When a wide viewing angle characteristic is obtained by applying no voltage to the viewing angle control device 120, an image (partial view (A)) displayed on the liquid crystal display element 112 is visually recognized.
When a viewing angle characteristic that is difficult to view from a wide viewing angle is obtained by applying a voltage to the viewing angle control device 120, the viewing angle control device 120 uses a liquid crystal in a region corresponding to the pattern of the electrode 122. Molecules change the alignment direction in a direction perpendicular to the substrate 121. Therefore, as described above, the pattern of the electrode 122 is visually recognized from an oblique direction (partial view (B)). At this time, since the birefringence effect is not generated from the front direction, only the image (partial view (A)) displayed on the liquid crystal display element 112 is visible, but from the oblique direction, the liquid crystal display element 112 is viewed. The displayed image and the pattern displayed by the viewing angle control device 120 are visually recognized in an overlapping manner (part (C)). Overlapping displays can be visually recognized in any of the vertical and horizontal directions.

  The size of the pattern of the viewing angle control device 120 is preferably 1/2 to 2 times the size of characters displayed on the liquid crystal display element 112. More preferably, the size of the pattern of the viewing angle control device 120 is substantially the same as the size of characters displayed on the liquid crystal display element 112. As shown in FIGS. 4, 5, and 6, when the character size of the pattern of the viewing angle control device 120 is equal to the character size of the display of the liquid crystal display element 112 (FIG. 4), it is doubled. (FIG. 5), compared with the case of halving (FIG. 6), it is possible to further prevent the user from recognizing characters.

  At this time, it is preferable that the characters displayed on the liquid crystal display element 112 overlap with each other. This can make it difficult to visually recognize the characters on the display device from an oblique direction.

  For example, the display device 100 of the present invention is suitable for a mobile phone. In particular, it is suitable for the case where an unspecified person can be present near the user, for example, when mail display is performed with a mobile phone in an urban area (indoor or outdoor) or transportation. The mail function of a mobile phone generally uses characters of a certain size. Also, the display interval is generally constant. Therefore, by disposing a pattern substantially the same as the character size in the viewing angle control device 120 at a position corresponding to the character of the liquid crystal display element 112, it is possible to make it difficult to visually confirm from an oblique direction.

  Also, in mail, display is mainly performed in hiragana and kanji. Therefore, visual recognition becomes difficult by superimposing the same type of characters. Hiragana is difficult to be visually recognized because it has many curved portions and a complicated pattern. Examples of characters that can be used in the present invention include katakana, kanji, alphabets, numbers, and symbols. Examples of the present invention are shown below.

  The display device 100 was manufactured by changing Δnd of the liquid crystal layer 125 of the viewing angle control device 120 to 1.2 μm, 2.4 μm, and 3.6 μm by the method as described above.

  As shown in FIG. 4, Table 1 shows the visible range when the normal direction of the main surface (display surface) of the display device 100 is 0 ° and the viewing angle θ is changed.

  When a voltage is applied between the electrodes of the viewing angle control cell to make the direction of the liquid crystal molecules vertical, the viewing angle becomes narrow according to the value of Δnd. When Δnd is increased, the viewing angle can be further narrowed.

  Further, when examining the effect of the display and the luminance of the background at the time of display, if the display of the same or close to the background luminance and the display luminance is performed in the viewing angle control cell, the viewing angle control effect is enhanced. This is shown in Table 2.

  In this way, the viewing angle can be controlled by performing the same display with the same size as the display size performed by the liquid crystal display element in the viewing angle control cell in which the liquid crystal is aligned in parallel.

It is typical sectional drawing of an example of the display apparatus concerning this invention. It is typical sectional drawing of the viewing angle control apparatus in the display apparatus concerning this invention. It is a disassembled perspective view which shows the relationship between the liquid-crystal orientation direction of the viewing angle control apparatus in the display apparatus concerning this invention, and the transmission axis of a polarizing layer. It is explanatory drawing which shows the display state of the display apparatus concerning this invention. It is explanatory drawing which shows the display state of the display apparatus concerning this invention. It is explanatory drawing which shows the display state of the display apparatus concerning this invention. It is explanatory drawing which shows the display state of the conventional viewing angle control apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Display apparatus 110 Display element 111 Backlight unit 112 Liquid crystal display element 120 Viewing angle control apparatus 121a 1st board | substrate 121b 2nd board | substrate 122a 1st electrode 122b 2nd electrode 123a 1st orientation film 123b 2nd orientation Film 124 Sealing material 125 Liquid crystal layer 126 Polarizing layer

Claims (9)

The viewing angle control device and the display element are display devices arranged so that their respective display surfaces overlap,
The viewing angle control device includes a portion whose transmittance and / or color can be changed by an electric signal from the outside so that characters are visually recognized in a specific viewing angle direction.
From the main viewing angle direction, the characters are not visually recognized, the display of the display element is visually recognized,
A display device configured such that in a specific viewing angle direction, characters of the viewing angle control device and the display of the display element appear to overlap each other. The characters constitute a meaningful sentence;
The display device according to claim 1. The characters are hiragana,
The display device according to claim 1. The character is 1/2 to 2 times the size of the character appearing on the display of the display element.
The display device according to claim 1, 2 or 3. The character is substantially equivalent to the size of the character appearing on the display of the display element.
The display device according to claim 1, 2 or 3. The character is presented using a difference in optical effect depending on a viewing angle direction of an optical substance provided in the viewing angle control device.
The display device according to claim 1, 2, 3, 4, or 5. The character is formed by controlling the orientation of an optical substance exhibiting birefringence corresponding to the shape of the character.
The display device according to any one of claims 1 to 6. The viewing angle control device is a liquid crystal display element in which a liquid crystal layer is sandwiched between a pair of substrates with electrodes,
The liquid crystal of the liquid crystal layer has a parallel alignment,
Δn · d of the liquid crystal layer is 1.0 μm or more,
The display device according to claim 1. The viewing angle control device is provided with a polarizing layer having a transmission axis parallel or perpendicular to the alignment direction of the liquid crystal.
The display device according to claim 8.

Images