JP2010113257A - Liquid crystal display device and electronic shelf tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that when a bar code is displayed on a liquid crystal panel and is read with a bar code reader using a laser beam as a light source, the reading angle is narrow. <P>SOLUTION: The liquid crystal display device includes: a liquid crystal cell having a liquid crystal sealed between a pair of substrates and having a pair of polarizing plates disposed on the respective faces; and a white film disposed, with an air layer interposed, on the polarizing plate mounted on the substrate in the opposite side to the side to be irradiated with light for reading a bar code, the white film having a reflectance of not less than 90% and composed of a thermoplastic resin in which a large number of fine cells are formed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device and an electronic shelf label, and in particular, is arranged near a product display shelf in a store or the like, and displays information related to a product such as a product name, a product price, and a barcode at an arbitrary position. The present invention relates to a liquid crystal display device for improving the reading performance of a bar code display by a bar code reader and at the same time making it possible to achieve both display performances.

  A shelf label for displaying the price of a product displayed on the shelf is attached to a product display shelf of a store such as a supermarket or a convenience store. In order to save labor and time for changing the shelf label, the electronic shelf label and the electronic shelf label system connect the host computer and the store server of each store, and the product information transmitted from the host computer is stored on the display shelf in the store. A method of transmitting to an electronic shelf label is used.

  Japanese Patent Laid-Open No. 2008-161297 (Patent Document 1) discloses a display that displays the price of a product, a communication unit that communicates with a management device that manages information displayed on the display, and a liquid crystal display. In an electronic shelf label comprising a product sheet printed with a barcode identifying the product name or product and a shelf label sheet printed with a unique shelf label code identifying the display, An example in which the product sheet and the shelf label sheet are arranged on the same side as the display surface of the display and the product sheet is arranged so as to overlap the shelf label sheet in a plan view is disclosed, and the barcode is displayed on the electronic shelf label. Explains the necessity.

  Japanese Patent Laid-Open No. 2003-222893 (Patent Document 2) discloses an example of a technique for directly displaying a barcode on a liquid crystal display device of an electronic shelf label.

The reflective liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 7-84255 (Patent Document 3) relates to a reflector used in a display device of a portable electronic device such as a calculator, an electronic notebook, or an electronic timepiece. Explains the technology. A reflection plate is disposed on the back side of the liquid crystal cell. As the reflection plate, a reflection plate in which Al (aluminum) is vapor-deposited on the surface of a base sheet made of a resin film (hereinafter referred to as an Al vapor deposition reflection plate). The directivity of a reflector made of Al foil (hereinafter referred to as an Al foil reflector) is improved.
JP 2008-161297 A JP 2003-222893 A JP 7-84255 A

  However, when the present inventors tried to read a barcode with a barcode reader using a laser beam as a light source by displaying the barcode on a liquid crystal panel as in JP-A-2003-222893, the reading angle is It turned out that there was a problem of staying in a narrow angle range in front. Similar results were obtained with a bar code reader using LED illumination and a CCD image sensor in addition to laser light. The reading angle of the printed barcode described in Japanese Patent Application Laid-Open No. 2008-161297 can be read over a wide range from the front, which is a problem caused by the liquid crystal display device.

  In addition, a liquid crystal panel with a narrow angle range that can be read by this barcode reader is built into an electronic shelf label and attached to a product display shelf, and the reading work with the barcode reader is verified. It is difficult to work while standing on the shelf label attached to the rack. In the case of tall shelves, there were cases where reading was not possible without holding the barcode reader in front.

  Further, a reflector having directivity at an angle deviated from the regular reflection direction described in JP-A-7-84255 or a directivity in the regular reflection direction described in the prior art disclosed in JP-A-7-84255. It is very dark and difficult to read when the liquid crystal panel using an Al vapor deposition reflector with a light is attached to a low shelf near the floor of the product display shelf under ceiling lighting and the display on the liquid crystal panel is observed while standing in front.

  Similarly, when the liquid crystal panel is mounted on a shelf higher than the position of the human eye of the commodity display shelf under the ceiling lighting and the display on the liquid crystal panel is observed while standing in front, it becomes very dark and difficult to read.

  In order to solve the above-described problems, the present invention provides a liquid crystal display device in which a pair of substrates each provided with an electrode on the inner side, a liquid crystal sealed between the pair of substrates, and a pair of polarizations on both surfaces of the pair of substrates. Spectral reflectance at a wavelength of 450 to 750 nm is 90% through the air layer on the side of the polarizing plate attached to the liquid crystal cell in which the plate is arranged and the substrate opposite to the side irradiated with the light for reading the barcode. A white film made of a thermoplastic resin having a large number of fine bubbles formed therein was disposed.

  Also, the transmission axis direction of the polarizing plate on the side irradiated with the light for reading the barcode is in the range of 20 ° to 70 ° with respect to the short side direction of each bar constituting the barcode. did.

  The liquid crystal display device is a memory-type liquid crystal panel having a first stable state and a second stable state, and the liquid crystal molecule major axis direction is within 5 ° between the pair of substrates in any stable state. Therefore, the molecular long axis direction of the first stable state and the transmission axis direction of the polarizing plate were approximately 45 °.

  The liquid crystal display device is incorporated in a case of an electronic shelf label, and the case has a transparent cover that covers the display area side of the liquid crystal display device, and the retardation due to the birefringence of the transparent cover is adjusted to the wavelength of light for reading the barcode. In contrast, the thickness was set to 130 nm or less.

  In addition, the liquid crystal display device is incorporated in a case of an electronic shelf label, and the case has a transparent cover that covers the white film side opposite to the display area side of the liquid crystal display device. The liquid crystal display device can be displayed in the transmission mode.

  According to the electronic shelf label incorporating the liquid crystal display device of the present invention, since the reading angle of the displayed barcode is widened by the barcode reader, it is possible to accurately read and the product to which the electronic shelf label is attached There is no restriction on the reading posture depending on the height of the display shelf, which contributes to the improvement of work efficiency.

  Further, since there is no dependency on the reading with respect to the polarization direction inherent to the laser-type barcode reader, the types of barcode readers that can be used can be expanded and the convenience can be provided. Based on the same principle, the display of the electronic shelf label can be visually recognized even if polarized sunglasses are used in the store.

  In addition, the liquid crystal display device has a memory property, but it has a wide viewing angle, and since it can closely contact the air layer with a white film that does not have directivity and the air layer at a minimum distance, the influence of parallax can be minimized. The viewing angle range can be widened to ensure brightness.

  In addition, depending on the height of the product display shelf, it can be used in reflection mode for low shelves close to the floor and external light from the back for high shelves, and can be used with the co-operation of reflection mode and transmission mode. It can improve the decline of sex.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a liquid crystal display device according to the present invention. In FIG. 1, a liquid crystal panel 9 is formed such that an upper transparent electrode 3 and a lower transparent electrode 5 sandwich a liquid crystal layer 4. The upper transparent electrode 3, the liquid crystal layer 4 and the lower transparent electrode 5 are formed of an upper transparent substrate 2. The upper transparent substrate 2 and the lower transparent substrate 6 are sandwiched between the upper polarizing plate 1 and the lower polarizing plate 7. The upper polarizing plate 1 side is the side irradiated with light for reading the barcode. A white film 8 is installed under the lower polarizing plate 7 through an air layer.
The liquid crystal layer 4 is a reflective liquid crystal display device using a nematic liquid crystal having a memory property (not shown).

  Particularly important points in the above configuration are the thickness of the air layer and the characteristics of the white film 8. The white film is not particularly limited as long as the spectral reflectance at a wavelength of 450 to 750 nm is 90% or more. For example, a material in which many fine bubbles are formed inside a thermoplastic resin has a high light reflectance and can be used. This film appears white with non-directional reflection. The thermoplastic resin is not particularly limited as long as it can form a film by melt extrusion, but preferred examples include polyester, polyolefin, polyamide, polyurethane, polyphenylene sulfide and the like.

  However, even a white film having a spectral reflectance of less than 90% at a wavelength of 450 to 750 nm, such as a copy sheet having a spectral reflectance of around 70%, can solve the problem of a narrow reading range. . However, when the spectral reflectance is lowered, the contrast is lowered and the visibility is deteriorated.

  Specific examples of the polyester include polyethylene terephthalate (hereinafter abbreviated as PET), polyethylene-2,6-naphthalenedicarboxylate (hereinafter abbreviated as PEN), polypropylene terephthalate, polybutylene terephthalate, poly- 1, 4-cyclohexylene dimethylene terephthalate and the like can be mentioned.

  As the above-mentioned fine bubbles, those produced by a known method, for example, (1) a polyester resin and an incompatible thermoplastic resin were added, and after melt extrusion, the film was stretched uniaxially or biaxially. And (2) those obtained by adding organic or inorganic fine particles and melt-extrusion and then stretching uniaxially or biaxially. In the present invention, it is more preferable to increase the reflective interface by forming fine bubbles. That is, the one produced by the above method (1) or (2) is more preferred.

  The white film can be easily obtained on the market, and examples thereof include a reflective film of Toray Industries, Inc., Lumirror E60L type, E60V type, E6L type, and 6SV type. Even a Lumirror E20 type to which white inorganic fine particles are added may be used although it is inferior in performance. In addition, there is no problem even if similar products from other companies are used.

  FIG. 2 is a view for explaining the characteristics of the white film 8 of the liquid crystal display device according to the present invention. The upper part of FIG. 2 is the surface of the white film 8 taken by a micrograph, and the lower part of FIG. 2 is a profile of the surface of the white film 8 described above. The vertical axis direction represents the surface roughness, and the horizontal axis direction represents the scanning direction. The Lumirror E60L type was observed with a metal microscope, and the result of measuring the surface profile of the texture is shown. The surface has fine irregularities due to fine bubbles. Due to the unevenness, an air layer is effectively secured even if the white film 8 is lightly pressed against the polarizing plate. Since an air layer can be secured without using spacers such as beads, it is a very convenient material for assembly.

  Here, the reason why the white film 8 is employed in the liquid crystal display device according to the present invention will be described. Since the white film 8 has fine irregularities on the surface, an air layer is secured. The air layer is formed between the lower polarizing plate 7 and the white film 8, and light is refracted in the air layer when a region longer than the wavelength of light is secured. By providing regions having different refractive indexes of light, the angle at which total reflection is not performed is in a wider range than that without an air layer. When the range of angles that do not totally reflect is widened, the incident light can be emitted from a wide angle, and thus visibility is improved. In addition, even when highly directional light is incident, thanks to the non-directional reflection that is the characteristic of white film, the light is output in a wide direction and is a highly directional laser used in barcode readers and the like. This is because the barcode pattern displayed on the liquid crystal display device 27 can be read stably even when reading.

In the embodiment of the present invention, the lower polarizing plate of the conventional bistable liquid crystal panel is peeled off, and the polarizing plate with a reflector manufactured by Nitto Denko Corporation, model F3205M, is reattached and read by a laser barcode reader. The angle dependence is measured. The type F3205M is obtained by bonding a reflecting plate and a polarizing plate deposited with Al on a mat-treated substrate. It is a general reflective polarizing plate and has directivity in the regular reflection direction. The direction measured by the present invention is shown in FIG. FIG. 3 is a diagram for explaining the measurement of the reading angle range of the barcode reader. The mode in which the measurement direction of the barcode reader 15 is moved to the longitudinal angle 17 of the bar of the barcode and the short side direction of the bar of the barcode 18 There are two types of measurement directions that move to angle 16.

In the present invention, the axis of the short side direction of the bar of the bar code 18 is the X axis, the axis of the long side direction of the bar code 18 is the Y axis, and the axis perpendicular to the plane on which the bar code is displayed is Z. Determined as the axis.

  The measurement results are shown in FIG. Here, the bar-side angle dependency of the reading performance of the white film of the liquid crystal display device according to the present invention and the conventional Al vapor deposition reflector was compared. This is an experiment of reading a barcode by tilting the barcode reader in the Y-axis direction. In FIG. 4, a square symbol indicates the number of successful readings of the Al vapor deposition reflector, and a circle symbol indicates the number of successful readings of the white film. The horizontal axis represents the inclination angle in the long side direction of the bar, and the vertical axis represents the number of successful experiments performed three times. In FIG. 4, reading was successful only in the range of −15 degrees to +15 degrees with the Al vapor-deposited reflector, whereas reading was successful all three times in the range of −35 degrees to +40 degrees with the white film. ing. From this result, it can be seen that the barcode can be read in a wider range in the white film than in the Al vapor deposition reflector.

FIG. 5 compares the dependence of the reading performance of the white film of the liquid crystal display device according to the present invention and the conventional Al-evaporated reflector on the short side direction angle of the bar. This is an experiment in which the barcode is read by tilting the barcode reader in the X-axis direction. Also in FIG. 5, as in FIG. 4, the square symbol indicates the number of successful readings of the Al vapor deposition reflector, and the circle symbol indicates the number of successful readings of the white film. The horizontal axis represents the inclination angle in the short side direction of the bar, and the vertical axis represents the number of successful experiments performed three times. In FIG. 5, all reading was successful only in the range of 0 ° to + 10 ° with the Al vapor-deposited reflection plate, whereas reading was successful all three times in the range of −35 ° to + 30 ° with the white film. ing.

4 and 5, it can be seen that the conventional Al vapor-deposited reflector has a narrow reading angle by a laser-type barcode reader. This is due to the following factors.

(1) Assuming a normal liquid crystal display, the light source is ceiling illumination and is viewed in the regular reflection direction with respect to the liquid crystal display reflector. On the other hand, since the bar code reader is close to the laser emission position of the light source and the photodetector, it cannot receive the light in the regular reflection direction that is almost reflected by the reflecting plate. In order to receive light, it is necessary to hold the barcode reader at an angle close to perpendicular to the reflector. If the angle deviates even a little, the detector cannot receive light.

  (2) Also, if the diffusibility of the reflecting plate is strengthened, if the polarizing plate and the reflecting plate are integrated, internal diffusion will occur, and when the diffused light is almost emitted, it will be entirely at the interface between the polarizing plate and the air. It cannot be reflected and emitted, and is eventually absorbed by the polarizing plate and darkens. As a result, less light is incident on the photodetector of the barcode reader, resulting in a decrease in detection sensitivity. Furthermore, since the brightness of the display also decreases, the visibility also decreases at the same time.

  (3) The parallax also contributes to the cause of the decrease in the dependency of the reading performance of the barcode reader on the angle of the short side direction of the bar. FIG. 6 shows a parallax generated when a barcode is displayed on a general liquid crystal display device and viewed from the front and obliquely. FIG. 6a shows the barcode 19 observed from the front, and FIG. 6b shows the barcode 20 observed from an oblique direction. Comparing FIG. 6a and FIG. 6b, it can be seen that a shadow is reflected when viewed obliquely. The influence of this shadow is obvious. If the reading angle of the barcode reader is tilted toward the short side of the bar, the reading angle becomes narrower due to parallax. As a countermeasure, it is effective to reduce the thickness of the glass and polarizing plate, but there is a limit to reducing the thickness.

  (4) The light of the laser bar code reader is linearly polarized light. In most barcode readers, the plane of polarization of light is set parallel to the long side direction of the bar. Or it may be parallel to the short side direction, but it is mostly the direction of these two. The angle of the upper polarizing plate of the liquid crystal display device needs to correspond to these two. If the linear polarization direction of the barcode reader and the transmission axis of the upper polarizing plate are shifted by 90 degrees, reading is impossible.

  In the present invention, the following countermeasures are taken against the four factors that reduce the reading angle of the laser bar code reader.

  For the above (1), a white film was adopted from a conventional Al vapor deposition reflector. The white film has a spectral reflectance of 90% or more at a wavelength of 450 to 750 nm, for example, a film in which many fine bubbles are formed inside a thermoplastic resin, has a high light reflectance, and has no directivity. It is a reflector.

  Here, FIG. 7 is a diagram for explaining a method of measuring the angle dependence of the retroreflectance. An angle of 6 ° with respect to the Z axis perpendicular to the XY plane of the barcode surface is set and fixed for the photodetector 21 and the laser 22. The angle dependence of the retroreflectance is measured by tilting the photodetector 21 and the laser 22 with respect to the Z axis in the range of −70 degrees to +70 degrees with the measurement sample 23 as the center. This measures the characteristics corresponding to the reading of a laser bar code reader.

  FIG. 8 compares the angle dependence of the retroreflectance of the white film of the liquid crystal display device according to the present invention and the conventional Al vapor deposition reflector. In FIG. 8, a circle symbol indicates a white film, a square symbol indicates an Al vapor-deposited reflector, and an incident angle is in the range of −70 degrees to +70 degrees with respect to the Z axis as described above. The incident angle is shown on the horizontal axis, and the retroreflectance is shown in percentage on the vertical axis. In FIG. 8, it can be seen that the Al-evaporated reflector has a retroreflectance exceeding 50% when the incident angle is in the range of −10 degrees to +10 degrees. At other angles, the retroreflectance is close to 0%. On the other hand, the white film is not greatly dependent on the incident angle, and as a whole, a high retroreflectance exceeding 80% is obtained in the range of −70 degrees to +70 degrees measured this time. The white film shows that the retroreflectance does not extremely decrease and does not have directivity even when the incident angle is increased as compared with the conventional Al vapor deposition reflector. Therefore, in the liquid crystal display device according to the present invention, the reflected light of the laser reaches the photodetector of the barcode reader even if the laser barcode reader is tilted.

For (2) above, the surface of the white film has fine irregularities due to fine bubbles. Because of the unevenness, an air layer is effectively secured even if the white film is lightly pressed against the polarizing plate. FIG. 9 is a schematic cross-sectional view for explaining the effect of the air layer.
FIG. 9A is a front view of the liquid crystal panel 9 and a diagram showing an XY plane. An air layer area 12 having an air layer between the lower polarizing plate of the liquid crystal panel 9 and the white film 8 and a transparent glue area 13 in which the white film 8 and the liquid crystal panel 9 are bonded together with a transparent glue. FIG. 9B shows a sectional view of the liquid crystal panel 9 and a ZX plane. A and B respectively indicate light incident paths. FIG. 9 compares the reflection of light with an air layer and the reflection of light with no air layer and filled with transparent glue.

The light A output from the barcode reader is reflected from the liquid crystal panel 9 by the white film through the air layer. The white film diffuses light without directivity. The light emitted from the liquid crystal panel 9 is refracted according to Snell's law and has an angle equal to the angle reflected by the white film.

Similarly, the light B output from the barcode reader is reflected from the liquid crystal panel 9 via the transparent paste 14 to the white film. The white film diffuses light without directivity. However, the refractive index of the liquid crystal panel 9 is around 1.5, and the refractive index of the transparent paste 14 is around 1.49. As is clear from comparison with the refractive index 2 in the atmosphere, the refractive indexes of the liquid crystal panel 9 and the transparent paste 14 are substantially equal, and the reflected light goes straight to the interface between the liquid crystal panel 9 and the outside without being refracted. . However, when this diffuse reflected light is emitted from the inside of the liquid crystal panel 9, light having an angle exceeding the critical angle of total reflection is confined inside. Only the region with a small angle can be emitted out of the liquid crystal panel 9 and, as a result, the reflected light of the laser reaching the photodetector of the barcode reader is reduced.

  For the above reason, in the white film of the liquid crystal display device according to the present invention, the reflected light of the laser efficiently reaches the photodetector of the barcode reader due to the effect indicated by the optical path A.

  In contrast to the above (3), in the present invention, when a white film is installed under the lower polarizing plate via an air layer, it is necessary to make the space between the air layers as thin as possible. If it becomes narrow, the effect of providing an air layer cannot be obtained sufficiently. The longest wavelength of visible light is around 0.8 μm. Considering the above conditions, it is desirable that the fine bubble diameter forming the air layer is a white film capable of maintaining the range of 1 μm to 10 μm even in a lightly pressed state. When Lumirror E60L type is used as a white film, the surface has fine irregularities due to fine bubbles. Because of the unevenness, an air layer is effectively secured even if the white film is lightly pressed against the polarizing plate. In this case, the effective interval is several μm or less. It can be made thinner than when using a spacer such as a bead to secure the interval. By taking the above measures, the occurrence of parallax can be reduced, and the reduction in reading angle dependency of the barcode reader can be improved.

  For the above (4), the transmission axis direction of the upper polarizing plate 1 on the side irradiated with the light for reading the barcode is set to 20 ° to the short side direction of each bar constituting the barcode. It was made to exist in the range of 70 degrees. FIG. 10 is a diagram for explaining the relationship between the polarization direction of the readout light of the barcode reader according to the present invention and the transmission axis of the upper polarizing plate of the liquid crystal display device. In FIG. 10a, the bar code reader 15 faces the liquid crystal display device 27 displaying the bar code in a shape perpendicular to the Z axis, and an arrow in the figure indicates a scanning range. FIG. 10 b is an XY plan view of the liquid crystal display device 27 displaying the barcode as viewed from the barcode reader 15. Here, a thick double arrow indicates the vibration direction of the laser, and the laser vibrates with respect to the X-axis direction. As will be explained again, the transmission axis direction of the upper polarizing plate 1 falls within the range of 20 to 70 degrees on the XY plane.

In most barcode readers, the plane of polarization of light is set parallel to the long side direction of the bar, or the two directions are mostly parallel to the short side direction. The angle of the transmission axis of the upper polarizing plate of the liquid crystal display device needs to correspond to these two. This is because reading is impossible if the transmission axis of the upper polarizing plate 1 is shifted by 90 degrees with respect to the polarization plane of one of the lights. In this invention, it was made to exist in the range of 20 degrees-70 degrees with respect to the short side direction of a bar. Within this setting, the decrease in transmittance due to the deviation between the polarization direction of the readout light and the transmission axis of the upper polarizing plate is stabilized at about half, which contributes to the stabilization of reading.

  As a result of the interaction of the above (1) to (4) interacting, as shown in FIGS. 4 and 5, the reading performance of the white film of the liquid crystal display device according to the present invention and the conventional Al vapor deposition reflector Comparing the long-side direction angle dependency of the bar, the white film of the liquid crystal display device according to the present invention can be read over a wide range as compared with the reading performance of the conventional Al vapor deposition reflector.

  On the other hand, the display appearance and visibility of the liquid crystal display device according to the invention were also improved. Since the white film employed in the liquid crystal display device according to the present invention exhibits a non-directional reflection characteristic, a liquid crystal mode having a large viewing angle dependency such as a TN liquid crystal that has been conventionally used for the liquid crystal mode used. However, when the viewing angle is large, there is a problem that the contrast is lowered and the inversion of black and white is easily seen. This problem is not a problem because the conventional Al-deposited reflector has high directivity, and when the viewing angle is large, the reflected light disappears and becomes dark and cannot be visually recognized.

  In the present invention, the liquid crystal display device is a memory type liquid crystal panel having a first stable state and a second stable state, and the liquid crystal molecule major axis direction has an angle of 5 with a pair of substrates in any stable state. The molecular long axis direction of the first stable state and the transmission axis direction of the polarizing plate were approximately 45 degrees. The white display unit 10 in FIG. 1 represents the second stable state, and the black display unit 11 represents the first stable state, and the angle between the white display unit 10 and the substrate is within 5 degrees. As a result, a wide viewing angle characteristic is obtained. Although not shown, since the angles of the upper polarizing plate and the lower polarizing plate are set to substantially parallel Nicols, the molecular long axis direction of the first stable state and the transmission axis direction of the polarizing plate are approximately 45. The black display with a wide viewing angle can be obtained by the degree.

  In this embodiment, a memory-type liquid crystal is used to display a barcode by matrix driving on the premise that it is used for an electronic shelf label. However, if the battery life is acceptable, a liquid crystal with a wide viewing angle and no memory property is used. A mode can also be used.

  Furthermore, the improvement point at the time of incorporating a liquid crystal display device in an electronic shelf label is demonstrated below. FIG. 11 is a schematic cross-sectional view (ZX plane) of the electronic shelf label of the present invention. The description of FIG. 11 will be given. The main part of the case 29 of the electronic shelf label is composed of a liquid crystal display device 27, a drive communication circuit 31 including an antenna and controlled by a CPU, and a battery 32. A liquid crystal display device 27 is connected to the drive communication circuit 31. In the case 29 of the electronic shelf label, a transparent cover 28 covering the display area side is arranged by molding. If the retardation value representing the amount of residual birefringence due to the molding of the transparent cover 28 is large, it affects the linear polarization of the light for reading the barcode, resulting in a problem that the transmittance of the upper polarizing plate of the liquid crystal display device is lowered. appear. In the present invention, the retardation due to the birefringence of the transparent cover is set to 130 nm or less with respect to the wavelength of light for reading the barcode. As a result, the change of the linearly polarized light stayed at about the circularly polarized light, and the fluctuation of the transmittance remained at about half at maximum, thereby preventing the deterioration of the barcode reading performance.

  Further, the cover 30 covering the white film side of the case 29 of the electronic shelf label may be made transparent as necessary. External light is taken in through the transparent cover, and the liquid crystal display device can be displayed in the transmission mode through the white film.

  FIG. 12 is a diagram for explaining a case where the electronic shelf label according to the present invention is used in a transmissive mode with the height of the commodity display shelf. Reflective electronic shelf labels 26 were installed on the shelves close to the floor, approximately 1 meter depending on the height of the merchandise display shelves. In this case, since it is not necessary to make the cover 30 covering the white film side transparent, the visibility of the display can be ensured by the high reflectance of the white film and the non-directional reflection. On the other hand, in a high shelf, a reflection / transmission co-help type electronic shelf label 25 that takes in external light from the back and uses the co-operation of the reflection mode and the transmission mode is installed. Visibility degradation due to the influence of lighting conditions can be improved. In this case, it is necessary to make the cover 30 covering the white film side transparent. Further, when a prism sheet is attached to the transparent cover, it becomes possible to efficiently take in external light.

  Also, even if the electronic shelf label is used in the transmission mode or the reflection mode depending on the height of the product display shelf, the barcode reading performance is not affected. Therefore, instead of switching the mode according to the height of the merchandise display shelf, it may be properly used depending on the environment, such as using a reflection / transmission co-help type electronic shelf label in an environment where the back is bright. In addition to the laser beam, a bar code reader using LED illumination and a CCD image sensor can be similarly improved.

  As described above, it is possible to provide an electronic shelf label that has a wide viewing angle and is not subject to the restriction of the height of an installation place, and has a wider reading angle dependency than a conventional barcode reader.

1 is a schematic cross-sectional view of a liquid crystal display device according to the present invention. It is a figure for demonstrating the characteristic of the white film of the liquid crystal display device which concerns on this invention. It is a figure explaining the measurement of the reading angle range of a barcode reader. It is the figure which compared the long side direction angle dependence of the reading performance of the white film of the liquid crystal display device which concerns on this invention, and the conventional Al vapor deposition reflector. It is the figure which compared the short side direction angle dependence of the bar of the reading performance of the white film of the liquid crystal display device which concerns on this invention, and the conventional Al vapor deposition reflector. It is a figure showing the state of the parallax which generate | occur | produces when displaying a barcode on a general liquid crystal display device and seeing from the front and diagonal. It is a figure explaining the measuring method of the angle dependence of a retroreflectance. It is the figure which compared the angle dependence of the retroreflectance of the white film of the liquid crystal display device which concerns on this invention, and the conventional Al vapor deposition reflective plate. It is typical sectional drawing explaining the effect of the air layer of a liquid crystal display device to this invention. It is a figure explaining the relationship between the polarization direction of the reading light of the barcode reader which concerns on this invention, and the transmission axis of the upper polarizing plate of a liquid crystal display device. It is a typical sectional view of the electronic shelf label of the present invention. It is a figure explaining the case where the electronic shelf label which concerns on this invention uses a transmission mode jointly by the height of a goods display shelf.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper polarizing plate 2 Upper transparent substrate 3 Upper transparent electrode 4 Liquid crystal layer 5 Lower transparent electrode 6 Lower transparent substrate 7 Lower polarizing plate 8 White film 9 Liquid crystal panel 10 White display part 11 Black display part 12 Air layer area 13 Area 14 Clear glue 15 Bar code reader 16 Bar short side direction angle 17 Bar long side direction angle 18 Bar code 19 Bar code observed from the front 20 Bar code observed from the diagonal 21 Photo detector 22 Laser 23 Measurement sample 24 Product Display shelf 25 Reflective / transparent electronic shelf label 26 Reflective electronic shelf label 27 Liquid crystal display device 28 Transparent cover covering display area side 29 Cover of electronic shelf label 30 Cover covering white film side 31 Drive communication circuit 32 Battery

Claims (6)

  Transparent electrodes are provided on the surfaces of the two transparent substrates facing each other, an alignment film is provided on the surface of the transparent electrodes, a liquid crystal layer is sandwiched between the two transparent substrates, and the outer sides of the two transparent substrates Each of the polarizing plates is disposed on the polarizing plate on the side of the transparent substrate that is not on the display surface side, and a spectral reflectance at a wavelength of 450 to 750 nm is 90% or more and a large number of fine bubbles are formed inside through the air layer. In a liquid crystal display device in which a white film made of a thermoplastic resin is arranged, the transmission axis direction of the polarizing plate on the side irradiated with light for reading the barcode is the short side of each bar constituting the barcode A liquid crystal display device having a range of 20 ° to 70 ° with respect to the direction.   The liquid crystal display device is a memory type liquid crystal panel having a first stable state and a second stable state, and the major axis direction of the liquid crystal molecule is an alignment film of the two transparent substrates in any stable state. 2. The liquid crystal display device according to claim 1, wherein the angle is within 5 °, and the angle formed between the molecular long axis direction of the first stable state and the transmission axis direction of the polarizing plate is approximately 45 °. .   3. The liquid crystal display device according to claim 1, wherein a diameter of the fine bubbles is within a range of 1 μm to 10 μm.   4. The liquid crystal display device according to claim 1, wherein the main component of the white film is a polyester film stretched at least in a uniaxial direction.   An electronic shelf label comprising the liquid crystal display device according to any one of claims 1 to 4 and a case incorporating the liquid crystal display device, wherein the case covers a display area side of the liquid crystal display device. An electronic shelf label comprising a transparent cover for covering, wherein retardation due to birefringence of the transparent cover is 130 nm or less with respect to a wavelength of light for reading the barcode.   The case has a transparent cover that covers the white film side opposite to the display area side of the liquid crystal display device, takes outside light through the transparent cover, and transmits the liquid crystal display device through the white film. 6. The electronic shelf label according to claim 5, wherein the electronic shelf label can be displayed in a mode.

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