JP2009128808A - Plasma display panel - Google Patents

Abstract

To provide a plasma display panel capable of achieving both improvement in reflection and improvement in sharpness and contrast of image light.
A plasma display panel includes a front plate and a back plate that are spaced apart from each other, a partition that partitions a discharge space formed between the front and back plates, and a partition. The phosphor layer 130 formed in the discharge cell 120 partitioned by 110, electrodes arranged on the front plate 200 and the back plate 100, respectively, and generating discharge in the discharge cell 120, and the viewer side of the front plate 200 In the plasma display panel 10 including the front filter 300 disposed on the front surface, the front filter 300 has fine irregularities on the surface on the viewer side and the surface on the front plate 200 side.
[Selection] Figure 1

Description

  The present invention relates to a plasma display panel, and more particularly to a plasma display panel in which a front filter is disposed.

  A self-luminous display such as a plasma display or a CRT display (cathode-ray tube display) is widely used because a natural image can be obtained without dependence on a viewing angle. In particular, the plasma display is rapidly spreading because it is thin and optimal for constructing a large screen.

  However, in various display devices including a plasma display, a reflection that reduces the visibility of a display image is often a problem. The reflection of the display device consists of a plurality of flat planes where the image of an indoor fluorescent lamp or an observer is on the side where the person observing the image is located (hereinafter referred to as the “observer side”). This is caused by being incident as external light and regularly reflected on the plane.

Therefore, a filter having an anti-reflection effect (anti-glare effect) has been conventionally proposed (for example, see Patent Document 1). The filter described in Patent Document 1 has a concavo-convex shape formed on the outermost surface by interspersing agglomerated portions of fine particles. By disposing the filter on the viewer side of the display device, external light can be diffusely reflected on the outermost surface of the filter, and reflection can be improved. Hereinafter, a filter having an antiglare action and disposed on the viewer side of the display device is referred to as a “front filter”.
JP-A-2005-316450

  However, when the front filter described in Patent Document 1 is used for a plasma display panel, there is a problem that the original image light is more unclear than a liquid crystal display. This is because the plasma display panel has a longer distance from the back plate that outputs the image light to the outermost surface of the front filter than the liquid crystal display, and sharpness due to diffusion when the image light passes through the outermost surface of the front filter. This is because the degree of reduction becomes larger.

  In addition, there is a problem that it is difficult to suppress reflection that occurs when external light entering the inside of the plasma display panel is regularly reflected on the surface of the front plate or the like. This is because the sensitivity of the refracted light to the degree of roughness of the outermost surface of the front filter is weaker than that of the reflected light, and if the outermost surface is roughened to improve the reflection due to internal reflection, surface diffusion increases. This is because the contrast of the image light is lowered.

  Therefore, in the plasma display panel using the front filter described in Patent Document 1, it is difficult to achieve both improvement in reflection and improvement in sharpness and contrast of image light.

  The present invention has been made in view of this point, and an object of the present invention is to provide a plasma display panel that can achieve both improvement in reflection and improvement in sharpness and contrast of image light.

  The plasma display panel according to the present invention is divided by a front panel and a rear panel that are spaced apart from each other, a partition that partitions a discharge space formed between the front panel and the rear panel, and the partition. A phosphor layer formed in a discharge cell, electrodes arranged on the front plate and the back plate, respectively, for generating a discharge in the discharge cell, and a front filter disposed on an observer side of the front plate; In the plasma display panel comprising the above, the front filter has a structure having fine irregularities on the surface on the viewer side and the surface on the front plate side.

  According to the present invention, external light entering the panel can be diffused not only on the surface of the front filter but also on the back surface, thereby suppressing the roughness of the surface of the front filter and improving reflection. be able to. In addition, the diffusion effect in the front filter can be more strongly applied to the external light that has entered the panel than to the image light. Thereby, it is possible to achieve both improvement in reflection and improvement in sharpness and contrast of image light.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic partial cross-sectional view of a plasma display panel according to an embodiment of the present invention. FIG. 1 shows a characteristic configuration of the plasma display panel according to the present embodiment, and the illustration and description of other parts are partially omitted.

  As shown in FIG. 1, the plasma display panel 10 includes a back plate 100, a front plate 200, and a front filter 300 that are spaced apart from each other and are stacked in parallel in this order. In the space between the back plate 100 and the front plate 200, a discharge space for generating plasma discharge is formed. A predetermined discharge gas mixed with helium (He), neon (Ne), xenon (Xe), argon (Ar), or the like is sealed in the discharge space. The space between the front plate 200 and the front filter 300 is an air layer.

  The back plate 100 is formed with a data electrode (not shown) covered with an insulator layer and a plurality of stripe-shaped partition walls 110 arranged in parallel with the data electrode. The discharge space described above is partitioned into a plurality of sections by the partition 110, and a plurality of discharge cells 120 serving as unit light emitting regions are formed. On the inner walls of three adjacent discharge cells 120, phosphors of red (R), green (G), and blue (B) are applied in different colors for each discharge cell to form a phosphor layer 130.

  Various components (not shown) for realizing the function as a plasma display panel, such as an electrode, a dielectric layer, and a protective film, are formed on the front plate 200 at appropriate positions. For example, although not shown, the front plate 200 is formed with a plurality of stripe-shaped display electrodes that are paired with scan electrodes and sustain electrodes, and a dielectric layer is formed so as to cover the display electrodes. A protective layer is formed. The dielectric layer is made of, for example, low-melting glass, and the protective layer is made of, for example, magnesium oxide (MgO).

  The front filter 300 includes, for example, a transparent plate 310 made of glass as a base material, and an electromagnetic wave shielding filter, an infrared cut filter, and a color adjustment filter (all not shown) are laminated on the transparent plate 310. The front filter 300 is further provided with a resin layer 320 made of a thermoplastic resin such as polyester as an antiglare layer on the viewer side of the transparent plate 310. The resin layer 320 is bonded to the transparent plate 310 via the adhesive layer 330.

  The front filter 300 has a surface uneven surface 340 constituting fine unevenness as an observer side surface, that is, an air interface of the resin layer 320. Further, the front filter 300 has a back surface uneven surface 350 constituting fine unevenness as a front surface 200 surface (hereinafter referred to as “back surface”), that is, as an air interface of the transparent plate 310.

  The uneven structure of the back surface uneven surface 350 is realized, for example, by performing uneven processing on the transparent plate 310. As the processing method, for example, frost processing, embossing, or sand blast processing is preferable. The uneven structure of the back surface uneven surface 350 is, for example, a flat surface on the front surface 200 of the transparent plate 310, and an antiglare resin film having an uneven structure made of a substance having substantially the same refractive index on the flat surface of the transparent plate 310. You may implement | achieve by adhere | attaching. However, when the concavo-convex processing is performed on the transparent plate 310, such an arrangement of the antiglare resin film becomes unnecessary, and there is an advantage that the front filter 300 can be configured with a minimum configuration.

  In the plasma display panel 10 configured as described above, when a voltage is applied between the electrodes, a discharge is generated in the discharge cell 120. For example, helium atoms in the mixed gas are excited to generate ultraviolet rays. Then, the phosphor layer 130 is excited by the ultraviolet rays, and visible light is generated.

  A part of the external light (hereinafter simply referred to as “external light”) that causes the reflection is reflected by the surface uneven surface 340.

  FIG. 2 is a diagram schematically showing the state of reflected light on the surface irregular surface 340.

  As shown in FIG. 2, since the surface uneven surface 340 has a fine uneven structure, the reflected light 410 of the external light 400 is diffused. Thereby, the reflection on the surface uneven surface 340 becomes irregular reflection, and as a result, the regular reflection on the viewer side surface of the front filter 300 which is the first cause of the reflection is reduced, and the reflection is reduced. That is, the degree of reflection due to the reflection on the surface uneven surface 340 is determined by the degree of diffusion (hereinafter referred to as “reflection diffusion”) due to the reflection of the surface uneven surface 340 on the reflected light.

  On the other hand, most of the outside light that has entered the panel without being reflected by the surface uneven surface 340 (hereinafter referred to as “entrance light”) is reflected by the back surface uneven surface 350 of the transparent plate 310 on the front plate 200 side. The reason why most of the incoming light is reflected by the back surface uneven surface 350 is that the refractive index difference in the back surface uneven surface 350 is large because the transparent plate 310 is in contact with the air layer.

  The reflected image is formed by combining the reflected light on the surface uneven surface 340 and the reflected light on the back uneven surface 350. In order to reduce the reflection, each reflected light must be sufficiently diffused.

  Conventionally, the air interface on the front plate 200 side of the transparent plate 310 is flat, and in order to reduce the influence of regular reflection of this flat surface, the incoming light that is the source of reflection reaches the flat surface described above. Before, it was necessary to scatter a lot. However, if an attempt is made to obtain a large diffusing action on the surface irregular surface 340, the sensitivity of the refracted light with respect to the degree of surface roughness is weaker than that of the reflected light, so the roughness of the surface irregular surface 340 must be increased. Don't be. If the surface diffusion of the surface uneven surface 340 is increased, the contrast reduction of the image light is also increased, which is not preferable.

  Therefore, in plasma display panel 10 according to the present exemplary embodiment, as described above, back surface uneven surface 350 is provided on front filter 300. Thereby, the degree of diffusion (hereinafter referred to as “refractive diffusion”) that the surface uneven surface 340 acts on the incident light is limited, and instead, reflection diffusion on the back surface uneven surface 350 is used. Thereby, the roughness of the surface of the front filter 300 can be suppressed and the reflection can be improved.

  FIG. 3 is a diagram schematically showing the state of incoming light reflected by the back surface irregular surface 350. Here, the refractive index of the resin layer 320, the adhesive layer 330, and the transparent plate 310 is substantially the same, and the reflection and refraction of the incoming light at each of these interfaces can be ignored.

  As shown in FIG. 3, the incoming light 420 that has entered the panel of the external light 400 is refracted while being diffused by the surface uneven surface 340, and then is subjected to a reflective action while being diffused by the back surface uneven surface 350. The reflected light 430 returns to the observer side and is refracted while diffusing again on the surface irregular surface 340. Thereby, the reflection on the back surface uneven surface 350 also becomes irregular reflection, and as a result, the regular reflection on the back surface of the front filter 300 which is the second cause of the reflection is reduced, and the reflection is reduced. That is, the degree of reflection due to reflection on the back surface uneven surface 350 is determined by the degree of diffusion that the back surface uneven surface 350 acts on incident light.

  Note that the image light from the display unit also passes through the surface uneven surface 340 and the back surface uneven surface 350 and is refracted on both surfaces. However, even on the same uneven surface, the diffusion effect due to refraction is weaker than the diffusion effect due to reflection, so that the reduction in the sharpness of the image light can be suppressed and the reflection can be improved.

  However, the sharpness of the image light is affected by the distance between the display unit and the diffusion surface, that is, the distance between the back plate 100 and the surface uneven surface 340. Therefore, it is necessary to control the degree of diffusion (hereinafter referred to as “diffusion condition”) acting on the image light transmitted through the front filter 300 according to this distance.

  Hereinafter, control of diffusion conditions in the plasma display panel 10 will be described.

  First, the distance that serves as a reference for controlling the diffusion conditions will be described.

  FIG. 4 is a diagram for explaining a distance serving as a reference for controlling the diffusion condition, and corresponds to FIG.

  Here, as shown in FIG. 4, the distance L that serves as a reference for controlling the diffusion conditions is defined as the distance from the phosphor layer 130 that is the display unit of the plasma display panel 10 to the surface uneven surface 340 of the front filter 300. To do. However, the distance L is an integrated value of values obtained by dividing the length occupied by each substance by the refractive index of each substance for the substances constituting the section from the phosphor layer 130 to the uneven surface 340 (hereinafter referred to as “air”). Conversion distance)). For example, the air conversion distance when 1 mm of glass having a refractive index of 1.5 and 1 mm of air having a refractive index of 1.0 are combined can be calculated as 1 / 1.5 + 1/1 = 1.67. .

  The image light from the phosphor travels to the viewer side while diffusing and is observed by the viewer. Since the image light is subjected to a diffusion action when passing through the back surface uneven surface 350 and the surface uneven surface 340, the sharpness of the image observed by the observer is deteriorated compared to the original image. The deterioration of sharpness increases as the air conversion distance L increases. This is because the transmissive area of light from the light source among the diffusing surfaces existing between the light source and the observer can be handled as a secondary light source, but usually the light from the light source is emitted in all directions and the secondary light source This is because the size of the light source increases as the distance between the diffusion surface and the light source increases, and the sharpness of the image of the light source decreases as the size of the secondary light source increases.

  Next, diffusion conditions for maintaining the sharpness of image light observed on the observer side will be described.

  Here, as an index representing the sharpness of the image light observed on the observer side, an MTF (modulation transfer function) which is an evaluation function indicating how much the original image sharpness can be reproduced is adopted. In particular, the MTF when the image light passes through the front filter 300 is referred to as “transmission MTF”.

  The highest spatial frequency to be reproduced in the image of the display device depends on the pitch of the display element, and is about 0.6 lp / mm (line pair per millimeter) for a plasma display panel of about 40 inches. Further, the lower limit value of the transmission MTF allowed as the sharpness of the image light is 0.7. Therefore, the transmission MTF = 0.7 is adopted at the spatial frequency of 0.6 lp / mm as the minimum value of allowable sharpness of the image light. When the transmission MTF is 0.7 or more, it can be considered that the sharpness of the image light is maintained.

  For example, when a front filter having a transmission MTF = 0.7 at a distance of 0.6 lp / mm is arranged on the front surface of a 42-inch plasma display panel at the same distance, there is no problem when observed from the front direction. When observed from an oblique direction, a reduction in the sharpness of the image is recognized. This is because the distance from the front filter to the phosphor layer when measured along the optical path to be observed is larger when observing from an oblique direction than when observing from the front direction. This is because the apparent transmission MTF is smaller than 0.7. Therefore, in the present embodiment, the transmission MTF of the front filter 300 is set to 0.7, but it is desirable that a transmission MTF of 0.7 or more can be ensured even at an angle from an oblique direction where an observer can observe an image.

  In addition, since the degree of reflection diffusion and the degree of refractive diffusion are proportional to the inclination angle of the fine portions of the unevenness, the diffuse transmission of all transmitted light when irradiated with visible light is used as a characteristic value indicating the diffusion condition of the front filter 300. A haze factor indicating the ratio of light is employed. The haze value of the entire front filter 300 is determined by the degree of refractive diffusion of the surface uneven surface 340 and the back surface uneven surface 350.

  FIG. 5 is a diagram showing the relationship between the air conversion distance L and the diffusion condition of the front filter 300 when the allowable minimum value of the sharpness of the image light observed on the observer side is determined.

  In FIG. 5, the horizontal axis indicates the air conversion distance L described in FIG. 4 in millimeters (mm), and the vertical axis indicates the haze value of the front filter 300 in percent (%). A point group 510 represented by a square plots a combination of an air-converted distance L and a front filter haze value HZ obtained by experiments and having a transmission MTF = 0.7 at a spatial frequency of 0.6 lp / mm. It is a thing. A point group 520 represented by a triangle plots a combination of an air-converted distance L and a front filter haze value HZ obtained by an experiment and having a transmission frequency MTF = 0.95 at a spatial frequency of 0.6 lp / mm. It is a thing. The transmission MTF indicates that the closer to the value “1”, the lower the degree of diffusion and the higher the sharpness of the image light.

The haze value HZ of the front filter 300 becomes infinite when the air conversion distance L is zero. Further, the transmission MTF of the front filter 300 does not decrease even when the air conversion distance L is infinite when the haze value HZ is zero. In addition, the regression curve can be regarded as sufficiently accurate when the square of the correlation coefficient exceeds 0.7. From these facts, it is assumed that the haze value HZ can be expressed by a polynomial of 1 / L, and the regression curve of the point group 510 is obtained by a polynomial approximation of the lowest order in which the square of the correlation coefficient exceeds 0.7. Then, the following equation (1) is obtained.

  A curve 530 represents the expression (1). That is, the curve 530 represents the contour line of the diffusion condition in which the transmission MTF = 0.7 at the spatial frequency of 0.6 lp / mm. The curve 530 takes a higher haze value as the air conversion distance L is shorter, and decreases with a quadratic curve as the air conversion distance L increases. Therefore, when the air conversion distance L is increased, in order to maintain the transmission MTF at 0.7 and maintain the sharpness of the image light, it is necessary to reduce the haze value of the front filter 300. There is.

Similarly, when the regression curve of the point group 520 is obtained, it is represented by the following equation (2).

  A curve 540 represents the expression (2). That is, the curve 540 represents the contour line of the diffusion condition where the transmission MTF = 0.95 at the spatial frequency of 0.6 lp / mm.

  The curve 540 is located on the lower left side of the curve 530 without intersecting the curve 530. Further, for example, when one value of the haze value HZ or the air conversion distance L is fixed and the other value is decreased, the transmission MTF naturally increases. That is, in the drawing, the left side or the lower side of the curve 530 is an area where the transmission MTF is higher than 0.7 and the sharpness of the image light can be considered to be maintained. The right side or the upper side of the curve 530 is an area where the transmission MTF is lower than 0.7 and it can be considered that the sharpness of the image light is not maintained.

Therefore, the sharpness of the image light is maintained when the haze value HZ of the front filter 300 satisfies the following expression (3).

  By configuring the front filter 300 so as to satisfy Expression (3), it is possible to prevent a reduction in the sharpness of the image light. That is, Expression (3) defines the maximum value of the haze value HZ of the front filter 300 according to the air conversion distance L from the display unit to the surface uneven surface 340 from the viewpoint of improving the sharpness of the image light. . When the haze value HZ of the front filter 300 exceeds the maximum value defined by the expression (3), the sharpness of the image light is lowered, which is not preferable as a display.

  In the present embodiment, as described above, it is possible to suppress the roughness of the surface uneven surface 340 correspondingly by diffusing a part of the reflected light that causes reflection in the back surface uneven surface 350. I have to.

  On the other hand, as another method of diffusing a part of reflected light that causes reflection, it is also conceivable to provide an internal diffusion layer that diffuses transmitted light inside the front filter 300 instead of the back surface uneven surface 350. However, it is possible to suppress the deterioration of the sharpness of the image light by using the back surface uneven surface 350 as in the present embodiment rather than using the internal diffusion layer. Hereinafter, as a reference, the difference from the case where the internal diffusion layer is used will be described.

  FIG. 6 is a schematic partial cross-sectional view of a plasma display panel using an internal diffusion layer, and corresponds to FIG. The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

  As shown in FIG. 6, the front filter 700 of the plasma display panel 60 includes, for example, a resin film composed of a resin layer 320 and an internal diffusion layer 730 on a transparent plate 710 having a flat air interface 750 on the front plate 200 side. The adhesive layer 330 is adhered and configured. The internal diffusion layer 730 imparts a diffusing action to transmitted light.

  FIG. 7 is a diagram schematically showing the state of reflected light on the surface uneven surface 340 of the plasma display panel 60.

  As shown in FIG. 7, the reflected light 410 of the external light 400 is diffused on the surface uneven surface 340, and as a result, reflection is reduced as described above. On the other hand, most of the incoming light that has entered the panel is reflected by the air interface 750 on the front plate 200 side of the transparent plate 710.

  FIG. 8 is a diagram schematically showing the state of incoming light reflected at the air interface 750.

  As shown in FIG. 8, the incoming light 420 that has entered the panel in the external light 400 is refracted by the uneven surface 340 before being reflected by the air interface 750 and diffused while being refracted by the internal diffusion layer 730. Affected. The incoming light 420 is further reflected at the air interface 750, and the reflected light 430 is also diffracted by the surface uneven surface 340 by receiving a diffusing action at the internal diffusion layer 730. As a result, when viewed from the observer side, the reflected light 430 appears to diffuse and reflect, and reflection is reduced.

  However, also in the plasma display panel 60, the sharpness of the image light from the display unit is lowered due to the refraction action and the diffusion action in the internal diffusion layer 730. Moreover, since the sensitivity of the refracted light is weaker than the sensitivity of the reflected light, in order to obtain the same reflection reduction effect as the plasma display panel 10 of the present embodiment in the plasma display panel 60, the internal diffusion layer 730 The degree of refractive diffusion must be higher than the degree of refractive diffusion of the back surface uneven surface 350. That is, even if a necessary declination is given by the back surface uneven surface 350, only about ¼ of the declination acts on the image light, whereas when a necessary declination is given by the internal diffusion layer 730, The same declination also acts on the image light. Further, when the internal diffusion layer 730 is used, the distance of the diffusion surface from the display unit becomes longer than when the back surface uneven surface 350 is used. Therefore, in the plasma display panel 60, the degree of reduction in sharpness is higher than in the case of the plasma display panel 10 of the present embodiment.

  As described above, according to plasma display panel 10 according to the present exemplary embodiment, front filter 300 has fine irregularities on the front and back surfaces on the viewer side. As a result, the external light entering the panel can be diffused not only in the reflection on the front surface but also in the reflection on the back surface, so that the surface roughness of the front filter 300 is suppressed and reflection is suppressed. can do. In addition, the diffusion effect on the front and back surfaces of the front filter 300 can be more strongly applied to external light than to image light. That is, the reflection can be suppressed in a state in which the sharpness and contrast of the image light are suppressed, and the sharpness is high without worrying about the reflection even when the plasma display panel 10 is installed in a bright place. Video can be provided.

  The plasma display panel according to the present invention is useful as a plasma display panel that can achieve both improvement in reflection and improvement in sharpness and contrast of image light.

1 is a schematic partial cross-sectional view of a plasma display panel according to an embodiment of the present invention. The figure which shows typically the mode of the reflected light in the surface uneven surface in this Embodiment The figure which shows typically the mode of the approach light reflected on the back surface uneven surface in this Embodiment The figure for demonstrating the distance used as the reference | standard of the control of the diffusion conditions in this Embodiment The figure which shows the relationship between the air conversion distance when the allowable minimum value of the sharpness of the image light observed on the observer side in this Embodiment is determined, and the diffusion conditions of the front filter Schematic partial cross-sectional view of a plasma display panel using an internal diffusion layer The figure which shows typically the appearance of the reflected light on the surface uneven surface of the plasma display panel which uses the internal diffusion layer The figure which shows the mode of the approach light which reflects at the air interface of the plasma display panel which uses the internal diffusion layer

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Plasma display panel 100 Back plate 110 Bulkhead 120 Discharge cell 130 Phosphor layer 200 Front plate 300 Front filter 310 Transparent plate 320 Resin layer 330 Adhesive layer 340 Surface uneven surface 350 Back surface uneven surface

Claims (6)

A front plate and a back plate that are spaced apart from each other;
A partition wall defining a discharge space formed between the front plate and the back plate;
A phosphor layer formed in a discharge cell partitioned by the barrier ribs;
Electrodes arranged on the front plate and the back plate, respectively, to generate discharge in the discharge cells;
A front filter disposed on the observer side of the front plate;
In a plasma display panel comprising:
The front filter is
The surface on the observer side and the surface on the front plate side have fine irregularities, respectively.
Plasma display panel. The front filter is
Either the most observer side or the most front plate side is formed of a resin layer, and the other is formed of a transparent glass plate with fine irregularities on the surface.
The plasma display panel according to claim 1. The front filter is
Both the most observer side and the most front plate side are formed of a resin layer,
The plasma display panel according to claim 1. The front plate side of the front filter is in contact with an air layer;
The plasma display panel according to claim 1. The front filter is
For the incoming light, a diffusion action is given at two places on the surface on the observer side and the surface on the front plate side.
The plasma display panel according to claim 1. The front filter is
The haze value is HZ, and is an integrated value of values obtained by dividing the length occupied by each substance with respect to the substance constituting the section from the phosphor layer to the surface on the observer side of the front filter divided by the refractive index of each substance. When the air conversion distance is L, the following equation is satisfied:
The plasma display panel according to claim 1.

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