JP2009146835A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a low-profile information terminal equipment display device having uniform brightness is difficult to realize. <P>SOLUTION: A lighting system with a transparent electrode consists of a light guide plate, the transparent electrode, a low-refractive-index resin layer provided between the light guide plate and the transparent electrode with its light refractive index smaller than that of the transparent electrode, and a prism formed on the light guide plate at the side of the low-refractive-index resin layer. The lighting system with the transparent electrode is provided as the front light of a reflection type liquid crystal display on the front face of the liquid crystal display. The electrode of a capacitance touch panel is formed on the transparent electrode. The transparent electrode of the lighting system with the transparent electrode is arranged in contact with the reflection type liquid crystal display. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display device with a lighting device, and more particularly to a display device in which a touch sensor function is incorporated in the lighting device.

As an input method for a recent information terminal device, a finger touch input method has been attracting attention.
In addition, a display device such as a liquid crystal display device is indispensable as the information terminal device.
A display device with a touch sensor can be considered as a combination of the two, but there is a problem that it is difficult to make the illumination of the display device uniform, because the entire display device becomes too thick.

In terms of thickness, the three mechanisms of a display device such as a liquid crystal display, an input detection device, and a lighting device are overlapped with each other, so that there is a problem that the thinning of the portable device is impaired. This problem is particularly problematic when a resistive film type touch panel is used because the input device is thick. For this reason, a capacitive touch sensor is preferable for thinning. However, this capacitive touch sensor is sensitive to noise because it needs to detect a very small current, and particularly when used for a capacitive display such as a liquid crystal display, it malfunctions due to the charge / discharge current noise of the display. There was a problem that.
Further, in terms of illumination uniformity, there is a problem that it is difficult to illuminate the entire display device almost uniformly.
This problem will be described with reference to FIG.

FIG. 7 is a partial cross-sectional view of a conventional illumination device with a touch sensor.
In FIG. 7, 12 is a light guide plate, 18 is a light emitting diode as a light source, 14 is a transparent electrode, and a capacitive touch sensor electrode, for example, can be formed on the layer 14.
When the light guide plate 12 is made of polycarbonate, the light refractive index is 1.585, and when the transparent electrode 14 is made of ITO, the light refractive index is 1.8. Therefore, the light is emitted from the light emitting diode toward the light guide plate 12 in FIG. As shown by 34 in FIG. 7, the light exits to the transparent electrode 14 side having a large light refractive index and does not reach the end of the light guide plate 12, that is, there is a problem that uniform illumination cannot be performed.
The transparent electrode pattern of the capacitive touch sensor is shown in FIGS.

A touch sensor using a light emitting diode as a light source is shown in FIG. 2 of Patent Document 2 in the same manner as FIG. 8 of this specification.
FIG. 8 is a perspective view showing a conventional illuminated touch sensor 200, and -0014- to -0017- generally have the following descriptions -0006- to -0009-.

  A light guide plate 230 that guides light for background illumination; an electrode layer 240 that is disposed under the light guide plate 230 and has at least one electrode pattern 241, 242 formed on one surface thereof that is in contact with the light guide plate 230; And at least one light source 221 and 222 that are disposed on side surfaces of the light plate 230 and the electrode layer 240 and generate light to be guided by the light guide plate 230. Preferably, the light sources 221 and 222 are side-emitting light emitting diodes.

  The electrodes (electrode patterns 241 and 242) of the electrode layer 240 include a conductive polymer or the like. Therefore, the electrode and the electrode layer 240 are made of a transparent material that can transmit light. The light guide plate 230 is preferably made of a dielectric material that can maintain the electric field generated on the electrode layer 240. In other words, the electrode layer 240 and the light guide plate 230 constitute a touch sensor that senses a change in current that constitutes an electric field generated through contact between a conductive object or a human body.

  In this embodiment, unlike the conventional configuration, since the light guide plate, the electrode, and the electrode layer are all formed using a transparent polymer material, the light guide plate and the transparent electrode layer are manufactured and bonded separately. Either a method or a method of printing a transparent electrode for a touch sensor on one surface of a light guide plate to manufacture a fully integrated type can be employed. In addition, since both the light guide plate and the electrode are transparent, the order in which the two layers are stacked in order to realize the function of the backlight is as shown in FIG. You may comprise in order of this, and may be comprised in order of the electrode layer 240-light-guide plate 230 from the reverse on the contrary.

  The light guide plate 230 may further include at least one diffusion pattern for diffusing the light with a uniform intensity, thereby guiding the light emitted from each of the light sources 221 and 222 to each of the diffusions. The light in the waveguide can be reflected outward by the pattern. In addition, the light guide plate 230 according to this embodiment is integrated with a substrate that covers the electrode layer of the touch sensor 240, so that a slim touch sensor device can be obtained. In addition, the light guide plate 230 may be integrated with the light sources 221 and 222 in the form of a flexible printed circuit board as another embodiment.

FIG. 3 of Patent Document 2 shows a cross-sectional view of a lighting device with a touch sensor, but it cannot be used as a front light of a liquid crystal display because a PCB is provided in the lower part.
Moreover, in the following drawings, the same number is attached | subjected to the same member and description is abbreviate | omitted.

Japanese Patent Application No. 2007-135634 JP2007-23458A

  The problem to be solved is that it has been difficult to realize a display device for information terminal equipment that is thin and has uniform brightness.

The display device according to the present invention includes a light guide plate, a transparent electrode, and a low refractive index resin layer having a light refractive index smaller than that of the transparent electrode between the light guide plate and the transparent electrode. A prism is formed on the low refractive index resin layer side to constitute a lighting device with a transparent electrode,
The illuminating device with a transparent electrode is provided in front of the liquid crystal display as a front light of the reflective liquid crystal display.

  The display device according to the present invention is characterized in that the transparent electrode is disposed on the liquid crystal display side.

  The display device according to the present invention is characterized in that an electrode of a capacitive touch panel is formed on the transparent electrode.

  In the display device according to the present invention, the transparent electrode includes two layers, a constant potential is supplied to the transparent electrode of one layer, and the transparent electrode is placed between the transparent electrode of the other layer and the liquid crystal display. It is a shielding layer against noise generated by the display.

  The display device according to the present invention includes a light guide plate, a transparent electrode, and a low refractive index resin layer having a light refractive index smaller than that of the transparent electrode between the light guide plate and the transparent electrode, A prism is formed on the low refractive index resin layer side to constitute an illumination device with a transparent electrode, and the transparent electrode of the illumination device with a transparent electrode is arranged so as to be in contact with a reflective liquid crystal display.

According to the present invention, since the transparent touch sensor and the illumination light guide plate function can be combined and integrated, a thin touch sensor with uniform brightness and a display device with illumination can be obtained. As a result, a display device compatible with a large screen can be realized.
Further, the display device can be easily provided with a touch sensor function, and the operation of the touch sensor can be stabilized.

A light guide plate, a transparent electrode, and a low refractive index resin layer having a light refractive index smaller than that of the transparent electrode is provided between the light guide plate and the transparent electrode, and on the low refractive index resin layer side of the light guide plate A prism is formed to constitute a lighting device with a transparent electrode, and the lighting device with a transparent electrode is provided on the front surface of the liquid crystal display as a front light of the reflective liquid crystal display. The transparent electrode is formed with an electrode of a capacitive touch panel. Further, the transparent electrode of the illumination device with the transparent electrode is disposed so as to be in contact with the reflective liquid crystal display.
Hereinafter, the present invention will be described based on examples.

FIG. 1 is a cross-sectional view of a lighting apparatus 10 with a transparent electrode used in the present invention.
In FIG. 1, 12 is a light guide plate, 18 is a light emitting diode as a light source, 14 is a transparent electrode, and, for example, a capacitive touch sensor electrode can be formed on the transparent electrode layer 14. Reference numerals 20 and 22 denote prisms formed on the upper and lower surfaces of the light guide plate 12. Reference numeral 16 denotes a low refractive index resin layer provided between the light guide plate 12 and the transparent electrode 14 and having a light refractive index smaller than that of the transparent electrode 14. is there.
The low refractive index resin layer 14 may be an adhesive layer that bonds the light guide plate 12 and the transparent electrode 14 together.
When the light guide plate 12 is made of polycarbonate, the light refractive index is 1.585. When the transparent electrode 14 is made of ITO, the light refractive index is 1.8. When the acrylic resin is used for the low refractive index resin layer 16, the light refractive index is 1. Since the critical angle between the light guide plate 12 and the low refractive index resin 16 is 71.15 °, if the lower surface prism 22 is formed and the angle of the incident light is changed, the light emitted to the transparent electrode side is reduced. By adjusting the amount, incident light can be guided to the end of the light guide plate 12 (the right end in the case of FIG. 1).
Here, the light guide plate may be formed of a relatively hard optical transparent substrate or a relatively soft optical transparent film.
In this configuration, the transparent touch sensor and the illumination light guide plate function are combined and integrated.

FIG. 2 shows an embodiment of the illumination device with a transparent electrode used in the present invention, and shows an example of the transparent electrode 14 in FIG.
The cross-sectional view of FIG. 2 differs from that of FIG. 1 in the transparent electrode 14, and the transparent electrode in FIG. 2 is composed of two layers of a layer 24 and a layer 26. Potential) is supplied and can function as a shield layer. Reference numeral 28 denotes a transparent electrode substrate, which is made of, for example, a transparent resin film.
Such a configuration is described in FIG. 5 and -0027- of Patent Document 1.

FIG. 3 is a cross-sectional view of an embodiment of the display device 100 according to the present invention.
In FIG. 3, reference numeral 30 denotes a reflective liquid crystal display, and the illumination device 10 with a transparent electrode is disposed on the front surface (upper surface) of the display 30 so that the transparent electrode 14 is on the liquid crystal display 30 side. The light emitted from the light emitting diode light source 18 is guided to the light guide plate 12 of the illuminating device with a transparent electrode 10 and then enters the reflective liquid crystal display 30 to illuminate the liquid crystal display 30, and then the reflective liquid crystal The light 32 is reflected by the display 30 and again passes through the illumination device 10 with a transparent electrode, and is recognized by the human eye 31.
Here, an electrode of a capacitive touch panel is formed on the transparent electrode 14.
The transparent electrode 14 is preferably composed of two layers as shown in FIG. 2. A constant potential is supplied to the transparent electrode of one layer and the transparent electrode 14 is placed between the transparent electrode of the other layer and the liquid crystal display 30. In addition, it serves as a shield layer against noise generated by the liquid crystal display 30.
Further, the transparent electrode 14 of the illumination device with a transparent electrode is disposed so as to contact the reflective liquid crystal display 30.

As described above, in the present invention, there can be realized a display device for an information terminal with a touch sensor that does not have a light blocking layer of the illumination device with a transparent electrode 10 and is thin and has uniform luminance.
Such an effect cannot be realized by mere application, although a PCB is disposed on the lower surface as in the illumination device with a transparent electrode disclosed in Patent Document 2.
Moreover, even if a capacitive touch sensor is used for thinning, the operation can be stabilized against noise generated by the liquid crystal display.
Of these, it should be noted that the transparent electrode is disposed in contact with the reflective liquid crystal display.

The data with uniform brightness is shown using FIGS.
FIG. 4 is a diagram showing luminance measurement points of the display device.
Basically, the luminance is measured at five points, i, b, c, d, and e, in a plan view from the side closer to the light-emitting diode light source to the far side.

FIG. 5 is a view showing a cross-sectional structure of a display device including a lighting device, a touch sensor, and a reflective liquid crystal display and measurement data. The touch sensor is formed on a transparent electrode. The touch position detection circuit of the touch sensor may be disposed on a side surface that avoids the optical path of light.
FIG. 5A is a diagram showing a cross-sectional structure of a conventional display device, in which a transparent electrode 14 is disposed below the light guide plate 12 and a reflective liquid crystal display (reflective LCD) 30 is disposed below the transparent electrode 14. .
In FIG. 5B, a low light refractive index resin layer 16 is provided between the light guide plate 12 and the transparent electrode 14.
In FIG. 5C, a lower surface prism 22 is further provided between the light guide plate 12 and the low light refractive index resin layer 16.

  FIG. 5D shows the luminance measurement data in the structure shown in FIG. 5C, and the luminance is further measured at five points in the Y direction for five points a, b, c, d, and ho. In the data, the brightest point is taken as 100%, and the brightness of other points is shown as a percentage of the 100%.

FIG. 6 is a graph plotting the average values of the points (I, B, C, D, E) of the luminance measurement data in each structure.
In FIG. 6, the vertical axis represents relative luminance, the horizontal axis represents the measurement position, 46 represents the luminance distribution in the structure of FIG. 5A, 48 represents the luminance distribution in the structure of FIG. 5B, and 50 represents the luminance distribution in FIG. The luminance distribution in the structure is shown.
As is apparent from the graph, in the conventional structure shown in FIG. 5A, as shown by the line 46, the brightness drops significantly as the distance from the light source increases. This indicates that light emitted from the light source hardly reaches the end of the light guide plate.
In the structure shown in FIG. 5B, the effect of providing the low-refractive-index resin layer 16 appears. As shown by the line 48, the right end of the graph, the point E, rises considerably, and the improvement effect is remarkable. It is.
In the structure shown in FIG. 5C, by providing the lower prism 22 in addition to the low light refractive index resin layer 16, the luminance distribution characteristics are greatly improved as shown by the line 50.
As described above, the low refractive index resin layer 16 having a lower light refractive index than the transparent electrode 14 is provided between the light guide plate 12 and the transparent electrode 14, and a prism is provided on the low refractive index resin layer side 16 of the light guide plate 12. By forming (that is, a lower surface prism), the luminance can be made uniform.

Note that although an example in which the lighting device is used as a front light of a liquid crystal display is shown in this specification, it can also be used for a backlight type.
In this case, it is a matter of course that the lighting device is placed on the lower surface of the transmissive liquid crystal display, and the transparent electrode for shielding is placed between the liquid crystal display and the touch sensor electrode.

It is sectional drawing of the illuminating device with a transparent electrode used by this invention. It is sectional drawing of one Example of the transparent electrode used by this invention. It is sectional drawing of the Example of the display apparatus by this invention. It is the figure which showed the luminance measurement point of the display apparatus. It is the figure and measurement data which showed the cross-section of the display apparatus which consists of an illuminating device, a touch sensor, and a reflection type liquid crystal display. It is the graph which plotted the average value of the brightness | luminance measurement data in each structure. It is a fragmentary sectional view of the conventional illuminating device with a touch sensor. It is the perspective view which showed the conventional touch sensor with illumination.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 Light-guide plate 14 Transparent electrode 16 Low refractive index resin layers 20 and 22 Prism 30 Liquid crystal display 100 Display device 26 Transparent electrode of one layer 24 Transparent electrode of other layer 28 Base material of transparent electrode

Claims (5)

A light guide plate;
A transparent electrode;
A low refractive index resin layer having a light refractive index smaller than that of the transparent electrode is provided between the light guide plate and the transparent electrode,
A prism is formed on the low refractive index resin layer side of the light guide plate to constitute a lighting device with a transparent electrode,
A display device, wherein the illuminating device with a transparent electrode is provided in front of a liquid crystal display as a front light of a reflective liquid crystal display.   The display device according to claim 1, wherein the transparent electrode is disposed on the liquid crystal display side.   The display device according to claim 2, wherein an electrode of a capacitive touch panel is formed on the transparent electrode.   The transparent electrode is composed of two layers, a constant potential is supplied to the transparent electrode of one layer, and the transparent electrode is placed between the transparent electrode of the other layer and the liquid crystal display, and shields against noise generated by the liquid crystal display. The display device according to claim 3, wherein the display device is a layer. A light guide plate;
A transparent electrode;
A low refractive index resin layer having a light refractive index smaller than that of the transparent electrode is provided between the light guide plate and the transparent electrode,
A prism is formed on the low refractive index resin layer side of the light guide plate to constitute a lighting device with a transparent electrode,
A display device, wherein the transparent electrode of the illumination device with a transparent electrode is disposed so as to be in contact with a reflective liquid crystal display.

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