WO2015033521A1

WO2015033521A1 - Touch panel

Info

Publication number: WO2015033521A1
Application number: PCT/JP2014/004203
Authority: WO
Inventors: 平岡　英敏
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2013-09-09
Filing date: 2014-08-18
Publication date: 2015-03-12
Also published as: JP2016191964A

Abstract

Provided is a touch panel that is disposed on the display screen of a liquid crystal panel and in which a light-emitting diode is used in a backlight, wherein the touch panel is provided with a main body at which a predetermined input operation is detected and an optical compensation sheet is formed on the main body. The optical compensation sheet has a retardation value of at least 1800 and less than 3000, and the angle formed by the slow axis of the optical compensation sheet and linearly polarized light exiting from the liquid crystal panel is approximately 45 degrees. By means of such a configuration, it is possible to achieve a touch panel such that viewing of the liquid crystal display screen is favorable.

Description

Touch panel

The present invention relates to a touch panel used on a display screen of a liquid crystal panel such as a portable information device, a car navigation system, or a camera.

In recent years, electronic devices in which a touch panel is arranged on the upper surface of a display screen of a liquid crystal panel of various electronic devices and a predetermined screen operation is performed with a user's finger or the like are widely used.

For example, Patent Document 1 is known as prior art document information related to the invention of this application.

JP 2006-79149 A

One embodiment of the present invention is a touch panel in which a light-emitting diode is used as a touch panel and is arranged on a display screen of a liquid crystal panel, and the touch panel includes a main body portion that detects a predetermined input operation, and a main body portion And an optical compensation sheet formed thereon. The optical compensation sheet has a retardation value of 1800 nm or more and less than 3000 nm, and an angle formed by the slow axis of the optical compensation sheet and linearly polarized light emitted from the liquid crystal panel is approximately 45 degrees.

According to the above configuration, the linearly polarized light emitted from the liquid crystal panel is eliminated by the optical compensation sheet.

The touch panel of the present disclosure has good visibility of the liquid crystal display screen even when the viewer wears polarized sunglasses or the like.

It is sectional drawing of the touchscreen by this Embodiment. It is a disassembled perspective view of the liquid crystal panel in which the touch panel by this Embodiment is mounted. It is a figure which shows an evaluation result.

Prior to describing the embodiment, conventional problems will be described.

On a liquid crystal display screen equipped with a conventional touch panel, the display on the liquid crystal display screen appears dark when the viewer wears polarized sunglasses or the like. In some cases, the display on the LCD screen is not visible.

This is because the light emitted from the liquid crystal panel is linearly polarized light, and the amount of light transmitted through the polarized sunglasses decreases as the polarization direction of the linearly polarized light coincides with or approaches the absorption axis of the polarized sunglasses. To do.

The present invention solves such a conventional problem, and provides a touch panel that has a simple structure and has good visibility of a display screen even when a viewer wears polarized sunglasses or the like. The purpose is to do.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.

(Embodiment)
FIG. 1 is a cross-sectional view of a touch panel according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view of a liquid crystal panel on which a touch panel according to an embodiment of the present invention is mounted. In order to make the configuration easy to understand, the touch panel 10 shown in FIGS. 1 and 2 is illustrated with an enlarged dimension in the thickness direction.

The touch panel 10 of the present embodiment is rectangular when viewed from above. The first detection sheet 1 and the second detection sheet 2 are stacked to constitute a main body 3. An optical compensation sheet 4 is further stacked on the upper surface of the main body 3 to constitute a touch panel 10. The touch panel 10 is pasted on the display screen 21 of the liquid crystal panel 20.

Each of the first detection sheet 1 and the second detection sheet 2 has an indium titanium oxide (ITO) film on the upper surface of a film-like base material made of an insulating resin having a light transmission property such as polyethylene terephthalate (PET) or polycarbonate. A transparent electrode (not shown) made of is formed in a predetermined pattern. Although not disclosed in FIGS. 1 and 2, the transparent electrode is connected to an electronic circuit (not shown).

The first detection sheet 1 and the second detection sheet 2 that are stacked constitute the main body 3. The touch panel 10 can be touched by the main body 3.

Next, the operation of the touch panel 10 mounted on the liquid crystal panel 20 will be briefly described. When a user touches a predetermined menu screen displayed on the display screen 21 of the liquid crystal panel 20 with a finger or the like via the touch panel 10, the first detection sheet 1 formed at a position corresponding to the operation position The electric capacity of the transparent electrode of the second detection sheet 2 changes. Then, the electronic circuit detects the change in the electric capacity, and the screen position operated by the user is specified, and a predetermined touch operation is performed.

The main body 3 in the present embodiment detects a position in the first direction (for example, a position on the X axis) with the first detection sheet 1 and a position in the second direction (for example, on the Y axis) with the second detection sheet 2. ) Is detected. And the main-body part 3 detects a plane position (X-axis position and Y-axis position) using these two detection sheets. The main body 3 is formed in a two-layer structure.

The optical compensation sheet 4 is formed of a polymer material such as polyethylene terephthalate (PET) in a sheet shape so as to have photo-orientation. An optical compensation sheet 4 is stuck on the upper surface of the main body 3. The optical compensation sheet 4 has a slow axis 4A in a predetermined direction and a predetermined retardation value.

In addition, the detail of the specific retardation value of the optical compensation sheet 4 in the present embodiment will be described later.

In the present embodiment, the light emitted from the display screen 21 of the liquid crystal panel 20 is linearly polarized light 21A, and the polarization direction is set to be parallel to the longitudinal direction (Y-axis direction) of the display screen 21. Yes.

The angle formed between the slow axis 4A of the optical compensation sheet 4 and the polarization direction of the linearly polarized light 21A of the liquid crystal panel 20 is set to 45 degrees.

In the present embodiment, the angle formed by the slow axis 4A of the optical compensation sheet 4 and the polarization direction of the linearly polarized light 21A of the liquid crystal panel 20 is 45 degrees, but if it is about 45 degrees ± 10 degrees, there is a problem. Absent. That is, the angle formed by the slow axis 4A of the optical compensation sheet 4 and the polarization direction of the linearly polarized light 21A of the liquid crystal panel 20 may be approximately 45 degrees.

With the above configuration, the linearly polarized light 21A emitted from the display screen 21 of the liquid crystal panel 20 is birefringent when it passes through the optical compensation sheet 4, and the linearly polarized light is eliminated.

In addition, it is preferable that the first detection sheet 1 and the second detection sheet 2 have a base material having low birefringence characteristics or no birefringence characteristics. However, when the first detection sheet 1 and the second detection sheet 2 are composed of a birefringent characteristic such as a stretched PET film, the slow axis of the first detection sheet 1 is shown in FIG. 1A and the angle formed by the polarization direction of the linearly polarized light 21A of the liquid crystal panel 20 and the angle formed by the slow axis 2A of the second detection sheet 2 and the polarization direction of the linearly polarized light 21A of the liquid crystal panel 20 are parallel or substantially parallel. The first detection sheet 1 and the second detection sheet 2 are stacked on the surface of the liquid crystal panel 20 so as to be set. As another embodiment, although not shown, the angle formed by the slow axis 1A of the first detection sheet 1 and the polarization direction of the linearly polarized light 21A of the liquid crystal panel 20 and the slow axis of the second detection sheet 2 are not shown. The first detection sheet 1 and the second detection sheet 2 are stacked on the surface of the liquid crystal panel 20 so that the angle formed by 2A and the polarization direction of the linearly polarized light 21A of the liquid crystal panel 20 is set at a substantially right angle. The

It should be noted that “substantially right angle” means that the angle does not have to be strictly right as long as it does not affect the product. The same applies to “substantially parallel”.

With the above configuration, the linearly polarized light 21 A emitted from the display screen 21 is decomposed into the slow axis 1 A component and the fast axis component corresponding to the slow axis 1 A when passing through the first detection sheet 1. Absent. Therefore, the first detection sheet 1 can be transmitted in the same polarization direction as that of the linearly polarized light 21A without the linearly polarized light being eliminated.

Similarly, the linearly polarized light that has passed through the first detection sheet 1 is not decomposed into the slow axis component corresponding to the slow axis 2A and the slow axis 2A when passing through the second detection sheet 2, The second detection sheet 2 can be transmitted.

Therefore, the linearly polarized light 21 A emitted from the display screen 21 can pass through the first detection sheet 1 and the second detection sheet 2 while maintaining the polarization direction of the linearly polarized light 21 A without eliminating the linearly polarized light.

And, at the time of transmitting through the first detection sheet 1 and the second detection sheet 2, the polarization direction of the linearly polarized light is the same polarization direction as the linearly polarized light 21A, birefringent when transmitted through the optical compensation sheet 4, Linear polarization is eliminated.

Therefore, in the liquid crystal panel on which the touch panel 10 of the present embodiment shown in FIG. 2 is mounted, a phenomenon that the display screen 21 becomes excessively dark even when the viewer wears polarized sunglasses or the like is suppressed. .

Next, the results of examining the relationship between the retardation value of the optical compensation sheet 4 of the touch panel 10 and the visibility of the display screen 21 in a state where the viewer wears polarized sunglasses or the like will be shown.

In this study, a white light emitting diode capable of producing a white display state was used as the light emitting diode. The liquid crystal panel 20 whose backlight (not shown) is a white light emitting diode was used, and the display state of the display screen 21 was examined in a white display state.

The touch panel 10 is configured by sequentially stacking the first detection sheet 1, the second detection sheet 2, and the optical compensation sheet 4 on the display screen 21 in the white display state. Light transmitted through the touch panel 10 was observed through the polarizing plate.

The absorption axis of the polarizing plate was set in parallel with the polarization direction of the linearly polarized light 21A emitted from the display screen 21. That is, in a state where the touch panel 10 is not arranged, all the light emitted from the display screen 21 is blocked by the polarizing plate.

In this study, a touch panel 10 having a plane size of 16 cm × 9 cm was used. Moreover, the 1st detection sheet 1 and the 2nd detection sheet 2 by which ITO was formed in the predetermined pattern on the upper surface of the base material by using the stretched PET film whose material thickness is 125 micrometers +/- 0.5 micrometer as the base material were used.

The stretched PET film is a material having birefringence characteristics. The retardation value of the first detection sheet 1 was 1785 μm, and the retardation value of the second detection sheet 2 was 1816 μm.

The slow axis 1A of the first detection sheet 1 and the slow axis 2A of the second detection sheet 2 were set in parallel with the polarization direction of the linearly polarized light 21A of the liquid crystal panel 20, respectively.

With this configuration, as described above, the linearly polarized light 21A emitted from the liquid crystal panel 20 can pass through the first detection sheet 1 and the second detection sheet 2 without the linearly polarized light being eliminated. it can.

That is, for the linearly polarized light 21A, the birefringence characteristics of the first detection sheet 1 and the second detection sheet 2 can be ignored. There is no need to select a material having no birefringence characteristics, and the degree of freedom in selecting a material can be widened. Furthermore, the influence on the linearly polarized light 21 A can also be reduced with respect to variations in the retardation values of the first detection sheet 1 and the second detection sheet 2 during mass production.

As the optical compensation sheet 4, samples 1 to 12 made of a stretched PET film having a thickness of 100 μm ± 0.5 μm and having different retardation values were prepared. For the above-described measurement of the retardation value, model WPA-1000 manufactured by Photonic Lattice was used.

The optical compensation sheet 4 may be any sheet having a predetermined retardation value in a state of being formed into a sheet shape. However, it is inexpensive if the optical compensation sheet 4 is made of a polymer material that is stretched into a film shape having a predetermined orientation, such as a stretched PET film. A desired retardation value can be easily realized by changing the stretching conditions of the stretched PET film.

Furthermore, a stretched PET film is preferable as a material constituting the touch panel 10 because it is excellent in punching processability by a press or the like and in a bending property in a sheet state.

In this study, the first detection sheet 1 and the second detection sheet 2 were fixed, and only the samples 1 to 12 of the optical compensation sheet 4 were replaced. And the evaluator observed the light which permeate | transmitted the touch panel 10 through a polarizing plate, and visually evaluated the visibility of a screen.

There are 10 evaluators, “◎” if all 10 people have judged that “Visibility is good and can be used”, “○” if 8-9, 5-7 Was evaluated in 4 grades, with “Δ”, 0 to 4 people, “x”. The evaluation results are shown in FIG.

As shown in the table of FIG. 3, the touch panel 10 using the

samples

1, 2, 4, and 6 for the optical compensation sheet 4 is judged by all 10 evaluators as “good visibility and usable”. The determination was “◎”, and it was determined that these touch panels 10 were non-defective.

Furthermore, in the touch panel 10 using the samples 3, 5, 7, and 8 as the optical compensation sheet 4, a slight rainbow-like color unevenness was observed from the center to the end of the screen, but there was no problem in practical use. Nine persons judged that “Visibility is good and can be used”, and the determination was “◯”. Note that the touch panel using Samples 3, 5, 7, and 8 was determined to be non-defective in actual use.

In the touch panel 10 using the sample 9, a slightly clear rainbow-like color unevenness was observed from the center to the end of the screen, and the determination was “Δ”, and it could not be determined to be a good product in actual use.

The touch panel 10 using the samples 10, 11, and 12 has clear rainbow-like color unevenness observed from the center to the end of the screen, and the determination is “x”, which is clearly a defective product in actual use. It was judged.

From the above evaluation results, the touch panel 10 using the samples 1 to 8 has a determination of “」 ”or“ ○ ”, and can be judged as a good product in actual use.

Therefore, it can be determined that the retardation value of the optical compensation sheet 4 is a non-defective product when the retardation value of the samples 1 to 8 is in the range of the retardation value (1783 nm to 3056 nm). From this evaluation result, the touch panel 10 using the optical compensation sheet 4 having at least a retardation value in the range of 1800 nm or more and less than 3000 nm can be judged as a non-defective product.

In addition, the touch panel 10 using the

samples

1, 2, 4, and 6 was judged as “◎”, and the one with better visibility was obtained. Therefore, if the retardation value of the optical compensation sheet 4 is set to a value in the vicinity of the retardation values of the

samples

1, 2, 4, and 6, the touch panel 10 with better visibility can be configured, which is more preferable.

In the touch panel 10, the judgment changed from “◯” to “△” between the sample 8 and the sample 9. In addition, although it is determined that a product with a determination of “Δ” cannot be a good product in actual use, the change in the visibility of the touch panel 10 is continuously changed according to the change in the retardation value of the optical compensation sheet 4. It is thought that it gradually changes from a good one to a deterioration direction.

Therefore, in the visibility of the touch panel 10, the boundary line between the retardation values that can be judged as good and those that cannot be judged is considered to be the retardation value between the sample 8 and the sample 9.

As described above, in the liquid crystal panel 20 on which the touch panel 10 of the present embodiment is arranged, the linearly polarized light 21 A emitted from the display screen 21 of the liquid crystal panel 20 is eliminated by the optical compensation sheet 4, and the viewer uses polarized sunglasses. Even in a state where the above is applied, the visual recognition of the display screen 21 is good.

In the above embodiment, the main body 3 that detects the touch operation is configured by stacking the first detection sheet 1 and the second detection sheet 2. However, the configuration of the main body 3 is not limited to the configuration of FIG. 1 or FIG. For example, a predetermined transparent electrode is formed on one base material, and a position in the first direction (for example, a position on the X axis) and a position in the second direction (for example, a position on the Y axis) are formed with only one detection sheet. ) May be a single-layer main body that can be detected. As another example of the configuration of the main body 3, the main body 3 may be configured by combining three or more detection sheets. What is necessary is just to set suitably the number of sheets and thickness of a detection sheet, the pattern of the transparent electrode formed in a base material, etc.

In addition, it is preferable that the materials of the detection sheets are designed without considering the slow axis of the detection sheet if a material having no birefringence characteristics is selected as described above. A material having birefringence characteristics may be selected. In this case, the slow axis of the detection sheet may be parallel or substantially parallel to the polarization direction of the linearly polarized light 21 A of the liquid crystal panel 20.

The angle formed by the slow axis of the detection sheet and the polarization direction of the linearly polarized light 21A emitted from the liquid crystal panel 20 is parallel in the present embodiment, but may have a slight angle difference from the parallel. That is, the angle formed by the polarization direction of the linearly polarized light 21 A emitted from the liquid crystal panel 20 may be substantially parallel.

Furthermore, the angle formed between the slow axis of the detection sheet and the polarization direction of the linearly polarized light 21A emitted from the liquid crystal panel 20 may be a right angle or may be slightly different from 90 degrees. That is, the angle formed by the polarization direction of the linearly polarized light 21 A emitted from the liquid crystal panel 20 may be substantially a right angle.

In the present embodiment, the angle formed by the slow axis of the first detection sheet 1 and the slow axis of the second detection sheet 2 may be substantially parallel. Furthermore, the angle formed by the slow axis of the first detection sheet 1 and the slow axis of the second detection sheet 2 may be substantially a right angle.

The retardation value of the detection sheet is set as appropriate.

Also, in the detection method of the main body unit 3 that detects an input operation to the touch panel 10, in the present embodiment, the method detects a change in capacitance, but is not limited thereto. As another detection method, there is a resistance film method in which a predetermined position is detected by pressing a main body configured by overlapping resistor sheets.

In the touch panel according to the present invention, the linearly polarized light emitted from the display screen is eliminated by the optical compensation sheet. Therefore, even when the viewer wears polarized sunglasses or the like, a touch panel with good visibility of the display screen can be realized, which is useful for operation units of various electronic devices.

DESCRIPTION OF SYMBOLS 1

1st detection sheet

1A, 2A, 4A Slow axis 2 2nd detection sheet 3 Main-body part 4 Optical compensation sheet 10 Touch panel 20 Liquid crystal panel 21 Display screen 21A Linearly polarized light

Claims

A light-emitting diode is used for the backlight, and the touch panel is arranged on the display screen of the liquid crystal panel.
The touch panel
A main body for detecting a predetermined input operation;
An optical compensation sheet formed on the main body,
The optical compensation sheet has a retardation value of 1800 nm or more and less than 3000 nm,
The touch panel, wherein an angle formed between a slow axis of the optical compensation sheet and linearly polarized light emitted from the liquid crystal panel is approximately 45 degrees.
The touch panel according to claim 1, wherein an angle formed by the slow axis of the main body and the linearly polarized light emitted from the liquid crystal panel is substantially parallel or substantially perpendicular.
The main body has a first detection sheet for detecting a position in the first direction, and a second detection sheet for detecting a position in the second direction,
The touch panel according to claim 2, wherein an angle formed by the slow axis of the first detection sheet and the slow axis of the second detection sheet is substantially parallel or substantially perpendicular.
The touch panel as set forth in claim 1, wherein the light emitting diode is a white light emitting diode.