JP2003240963A - Illuminator and display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display which is provided with an illuminator having a light transmission plate and capable of performing better display by suppressing a decrease in the visibility of a display picture in a display element caused by stripe ghost. <P>SOLUTION: The display AP1 comprises the illuminator LD1 having the light transmission plate 3 and a light source 5, and a reflection type liquid crystal display element LE1. The light transmission plate 3 has a light incident plane 31, prism plane 32 including a plurality of prism sections 32p, and a light- emitting plane 33. Each of the prism sections 32p consists of a slope 321 which is close to the light incident plane 31 and a slope 322 which is far away from the light incident plane 31. The slopes are in succession. The pitch of each of the prism sections 32p is of random. Any pitch P is in a range satisfying P=P<SB>0</SB>+ΔP and 2d<SB>0</SB>≤|ΔP|≤5d<SB>0</SB>. Where, P<SB>0</SB>is reference pitch; ΔP is variable width of reference pitch; d<SB>0</SB>is projection length to the light-emitting plane of the second slope of the virtual reference prism section in which pitch is P<SB>0</SB>. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device which can be used as a front light of a reflective liquid crystal display device. The present invention also relates to a display device including a lighting device.

[0002]

2. Description of the Related Art Display elements in portable devices such as mobile phones, PHSs, PDAs (personal digital assistants) and portable computers are required to be small, lightweight, thin and have low power consumption. A liquid crystal display element is known as a display element that can meet such a demand.

Since the liquid crystal display element is not a self-luminous type display element, illumination light is required for displaying. The liquid crystal display element is roughly classified into a transmissive type and a reflective type, and in each of them, display is performed as follows, for example.

In a display device using a transmissive liquid crystal display element, an illumination device called a backlight is arranged on the back side of the liquid crystal display element, and the light from the backlight is used as illumination light. An image is displayed by controlling the transmission of the light emitted from the backlight by the liquid crystal display element. Therefore, even when displaying in a bright place,
The backlight should always be on.

On the other hand, the display by the reflection type liquid crystal display element is such that outside light (sunlight, room light, etc.) is used in a bright place.
Can be visually recognized by using as an illumination light. Therefore, the reflective liquid crystal display element does not require an illuminating device in a bright place, and can achieve lower power consumption than a transmissive liquid crystal display device.

However, the display by the reflective liquid crystal display element is difficult to visually recognize in a dark place. Therefore, a display device including an illumination device called a front light for illuminating the observation side surface (front side surface) of the reflective liquid crystal display element has been proposed. By turning on the front light, the display by the reflective liquid crystal display element can be visually recognized even in a dark place.

As this front light (illumination device), one having a light source such as a cold cathode tube and a light guide plate for guiding light from the light source to a liquid crystal display element is known. The light guide plate is disposed on the observation side (front side) of the reflective liquid crystal display element that is the object to be illuminated (illumination target). The light from the light source enters the inside of the light guide plate from a predetermined incident surface, and is emitted as illumination light from an emission surface facing the liquid crystal display element. This allows
The liquid crystal display element is illuminated from its observation side (front side). In order to change the optical path of the light entering the light guide plate in this way, a plurality of prism portions are provided on the observation side of the light guide plate. Each prism portion has a light guide surface for guiding light entering the light guide plate from the incident surface in a direction away from the incident surface, and a reflecting surface for guiding the light to the exit surface. Since a plurality of fine prism portions are arranged on the light guide plate at a predetermined pitch, light is substantially uniformly emitted from the emission surface, and the liquid crystal display element that is the object to be illuminated can be illuminated substantially uniformly.

[0008]

However, a part of the light reflected by the reflecting surface of the prism portion and directed to the liquid crystal display element which is the object to be illuminated as illumination light is part of the light exit surface or the liquid crystal display element. The ghost light is reflected by the surface and travels toward the observer. A part of this ghost light is largely refracted by the reflecting surface of the prism portion, and becomes light that does not reach the observer. In other words, some of the ghost light does not enter the eyes of the observer,
The rest goes into the eyes of the observer. As a result, the ghost light is recognized by the observer as a striped ghost in which dark lines and bright lines (bright lines) are periodically arranged. The striped ghost obstructs the observation of the display image on the liquid crystal display element.

In addition to the above problems, in a reflective liquid crystal display device having a front light, moire fringes are generated by the periodic pattern of the prism portion of the light guide plate and the periodic pattern of pixels of the liquid crystal display element. Cheap. The moire fringes also hinder the observation of the display image on the liquid crystal display element and reduce the visibility of the display image.

Therefore, it is an object of the present invention to provide a light guide plate used in an illuminating device and capable of suppressing a reduction in visibility of an illuminated object due to a stripe ghost.

Another object of the present invention is to provide an illuminating device having a light guide plate, which is capable of suppressing a reduction in visibility of an illuminated object due to a striped ghost.

Further, the present invention is a display device including an illuminating device having a light guide plate and a display element, which can suppress deterioration of visibility of a display image of the display element due to a stripe ghost,
It is an object of the present invention to provide a display device which can display as good as that.

Further, the present invention is a display device provided with an illuminating device having a light guide plate and a display element, which can suppress the generation of moire fringes due to the prism pattern of the light guide plate and the pixel pattern of the display element, and thus a good display is achieved. An object of the present invention is to provide a display device capable of performing.

[0014]

[Means for Solving the Problems] §1. TECHNICAL FIELD The present invention provides a light guide plate, a lighting device, and a display device described below. The illumination device has a light guide plate and a light source. A display device has the above-mentioned lighting device and a display element, that is, has a light guide plate, a light source, and a display element. The light guide plate has the most characteristics, and the light guide plate will be mainly described below. The description regarding the light guide plate is similarly applicable to the illumination device including the light guide plate and the display device including the light guide plate.

§2. Light guide plate The light guide plate provided by the present invention has a light incident surface facing a light source, a prism surface including a plurality of prism portions, and a light exit surface on the opposite side of the prism surface. Each of the prism portions is composed of a first sloped surface close to the light incident surface and a second sloped surface distant from the light incident surface. In any prism portion, the first sloped surface and the second sloped surface are continuous. Therefore, the pitch of each prism portion is not constant but random, and the reference pitch serving as a reference of the pitch P of each prism portion is P ₀ , the increment / decrement width of the reference pitch is ΔP, and the pitch is the reference pitch P _0. When the projection length of the second inclined surface of the virtual reference prism portion on the light exit surface is d ₀ , the pitch P of any prism portion is P = P ₀ + ΔP, and 2d ₀ ≦ | ΔP Characteristic that it is within the range that satisfies the two conditional expressions of | ≦ 5d ₀ And the light guide plate.

§2.1. The light guide plate is for illuminating the illuminated object by performing light path conversion of the light emitted from the light source and emitting the light toward the illuminated object (illumination target) such as a display element. The light guide plate is plate-shaped (sheet-shaped) and has a light incident surface, a prism surface, and a light emitting surface.

The light incident surface is a surface corresponding to the side end surface of the light guide plate. The prism surface and the light exit surface are surfaces corresponding to the two surfaces (main surfaces) of the light guide plate, respectively. In other words, the prism surface is the surface opposite to the light exit surface, in other words,
The light exit surface is the surface opposite to the prism surface.

The light incident surface is exposed to the light source. The light emitted from the light source enters the light guide plate directly or indirectly through the light incident surface.

The light exit surface is a surface from which the light entering the light guide plate is emitted from the light guide plate toward the object to be illuminated. The light exit surface faces the object to be illuminated. The light exit surface may typically be a flat surface. The angle between the light exit surface and the light entrance surface is, for example, 9
It may be about 0 °.

The prism surface has a plurality of prism portions. The plurality of prism portions are arranged in a direction away from the light incident surface. Each prism portion is composed of a first slope and a second slope. The first inclined surface is arranged on the side closer to the light incident surface (the side closer to the light source), and the second inclined surface is arranged on the side farther from the light incident surface (the side farther from the light source). The first and second slopes are typically not parallel to the light exit surface and are inclined with respect to the light exit surface. Further, the first and second slopes are typically not parallel to the light incident surface, but are inclined with respect to the light incident surface.

The first inclined surface of each prism portion is mainly for guiding the light entering the light guide plate in a direction away from the light entrance surface (a direction toward the end surface on the light guide plate side opposite to the light entrance surface). is there. The light that is directly or indirectly incident on the first inclined surface is totally reflected by the first inclined surface, and this light is guided in a direction away from the light incident surface. The light exit surface is also used to guide the light entering the light guide plate by total reflection in the direction away from the light entrance surface.

The second inclined surface of each prism portion is mainly for guiding the light entering the light guide plate to the light exit surface. By reflecting the light directly or indirectly incident on the second inclined surface by the second inclined surface, this light is guided to the light emission surface and emitted from the light emission surface.

In each prism portion, the first slope and the second slope
The slope is continuous. That is, there is no flat surface (for example, a surface parallel to the light exit surface) between the first slope and the second slope that belong to the same prism portion. Further, in the two prism portions adjacent to each other (the side closer to the light incident surface is referred to as the first prism portion, the side farther from the light incident surface is referred to as the second prism portion), the second inclined surface of the first prism portion and the second prism portion The first slope of the prism portion is continuous. That is, there is no flat surface (for example, a surface parallel to the light exit surface) between the second inclined surface of the first prism portion and the first inclined surface of the second prism portion.

The pitch of each prism portion is not constant but random. The pitch P of any prism portion is in a range that satisfies the following two conditional expressions 1 and 2. P = P ₀ + ΔP (Equation 1) 2d ₀ ≦ | ΔP | ≦ 5d ₀ (Equation 2) Here, P ₀ is a reference pitch serving as a reference of the pitch P of each prism portion. ΔP is an increase / decrease width of the reference pitch (pitch fluctuation width). Further, d ₀ is the reference pitch P
It is a projection length of ₀ on the light emitting surface of the second inclined surface of the reference prism portion.

Since d ₀ > 0, ΔP ≠ 0, and the pitch P of any prism portion is P ≠ P ₀ .
That is, the reference prism portion having the pitch P ₀ does not exist on the prism surface, and the reference prism portion is virtual.

The projection length d ₀ is the angle α _{0 with} respect to the light exit surface of the second inclined surface of the reference prism portion and the height H ₀ of the reference prism portion (or the angle α ₀ and the light of the first inclined surface of the reference prism portion). It can be expressed by the following equation 3 depending on the angle β ₀ ) with respect to the exit surface. d ₀ = H ₀ / tanα ₀ (= P ₀ tanβ ₀ / (tanα ₀ + tanβ ₀ )) (Equation 3) Each prism portion of the light guide plate is not limited to this, and an illumination device including this light guide plate is used. Considering the use as an illumination device for illuminating a display element (a liquid crystal display element or the like), it is better not to be conspicuous so as not to hinder the observation of the display image by the display element.

Then, the reference pitch P ₀ is 0.2 because the criticality with which the pitch can be visually recognized by human eyes is about 0.2 mm.
It may be about mm or less. The smaller the reference pitch P _0, the less noticeable the pitch. However, if the pitch is made too small, the number of prisms will increase, and the light that has entered the light guide plate will exit from the light exit surface while the light guide distance is short, and light that is far from the light entrance surface (far from the light source). The amount of light emitted from the emission surface area decreases, and the area of the illuminated object far from the light source becomes dark. Further, if the pitch is too fine, it becomes difficult to manufacture the light guide plate itself. The reference pitch may be determined in consideration of these. Specifically, the reference pitch P ₀ may be selected from the range of 150 μm ≦ P ₀ ≦ 200 μm, for example. Also, the height H of the reference prism part
_{If 0} is set too high, the area of the second slope increases, the area where the illuminated illuminated object can be observed becomes small, and the visibility of the illuminated object (for example, the visibility of the display image of the display element) is hindered. The height H ₀ of the reference prism portion may be about 5 μm or less. More specifically, the height H ₀ may be selected from the range of 1 μm ≦ H ₀ ≦ 5 μm, for example.

The angle α ₀ of the second inclined surface of the reference prism part is
In order to change the optical path of the light incident on this slope toward the light exit surface, it may be about 45 °. More specifically, the angle α ₀ may be selected from the range satisfying, for example, 40 ° ≦ α ₀ ≦ 50 °.

For example, if the reference pitch P ₀ , the angle α _0, and the height H ₀ are respectively set to one value from the above range, the value of d ₀ is determined from the expressions 3 and the range of ΔP from the expression 2 is determined. Decided.

For example, the height H ₀ is set to 1 μm ≦ as described above.
H ₀ ≦ 5 μm, the angle α ₀ is 40 ° ≦ α ₀ ≦ as described above.
When the angle is 50 °, the projection length d ₀ is 0.
84 μm ≦ d ₀ ≦ 5.96 μm. In this case, the projection length d ₀ is minimum when H ₀ = 1 μm and α ₀ = 50 °, and is maximum when H ₀ = 5 μm and α ₀ = 40 °.

The above-described light guide plate has the following advantages because the pitch of each prism portion is not constant but random. When illuminating an object to be illuminated using this light guide plate, a part of the light reflected by the second inclined surface and directed to the light exit surface is reflected by the light exit surface or the surface of the object to be illuminated (light exit of the light guide plate). Reflected by the surface of the illuminated object facing the surface, a striped ghost in which dark lines and bright lines (bright lines) are lined up occurs. If the pitch of the prism portion is constant, a striped ghost in which dark lines are arranged at equal pitch occurs. When the object to be illuminated is a display device such as a reflective liquid crystal display device, the striped ghost in which dark lines are arranged at equal pitch significantly obstructs observation of the displayed image. On the other hand, by making the pitch of the prism part random, the periodicity of the dark lines of the striped ghost disappears, and compared with the case where striped ghosts in which dark lines of equal pitch line up occur, the display image by the striped ghost It is possible to suppress a decrease in visibility. In addition, | ΔP | 2d the fluctuation range of ₀
With the above, it is possible to prevent inclusion of a prism portion having a pitch in a range in which the amount of change from the reference pitch is small and a randomization effect is not sufficiently obtained, and stripe ghosts can be effectively reduced.

§2.2 The light guide plate will be further described. (A) The light guide plate may be made of, for example, a transparent resin such as an acrylic resin or a polycarbonate resin.
In this case, the light guide plate may be manufactured by molding, for example.

(B) To change the pitch of the prism parts, for example, the angle of the first slope, the angle of the second slope, the angle between the first slope and the second slope, and the height of the prism of each prism part. One or two or more of them may be changed.

In any case, the angle between the first slope and the second slope of the prism portion may be the same in any prism portion. With this configuration, when the light guide plate is manufactured by molding as described above, it is easy to manufacture a mold having a surface corresponding to the prism surface of the light guide plate, which is used for the molding. In this mold, the surface corresponding to the prism surface of the light guide plate is formed, for example, by cutting the flat surface of the mold member with a cutting member such as a cutting tool. If the angle between the inclined surface and the second inclined surface is the same, the cutting of the die member in the portion corresponding to any prism portion can be performed using the same cutting tool. Therefore, the die processing can be efficiently performed, and the die can be manufactured at a low cost.
Thereby, the light guide plate can also be manufactured at low cost.

(C) The light exit surface of the light guide plate may be subjected to antireflection treatment. That is, an antireflection film may be provided on the light exit surface of the light guide plate. By performing the antireflection treatment on the light exit surface, the reflection of light on the light exit surface is suppressed, the brightness of the ghost light itself is reduced, and the ghost light itself is less visible. As a result, the visibility of the illuminated object is reduced due to the ghost light (for example, the visibility of the display image of the display element is reduced).
Can be further suppressed. The antireflection treatment may be performed, for example, by applying an antireflection coating to the light emitting surface or by attaching an antireflection film to the light emitting surface.

§3. Illumination Device The illumination device (planar illumination device) of the present invention includes the above-described light guide plate and a light source facing the light incident surface of the light guide plate. That is, the illumination device according to the present invention includes a light source, a light incident surface facing the light source, a light guide plate having a prism surface including a plurality of prism portions and a light exit surface opposite to the prism surface, Each of the plurality of prism portions of the prism surface of the light guide plate is composed of a first sloped surface near the light incident surface and a second sloped surface far from the light incident surface. The slope and the second slope are continuous, the pitch of each prism portion is not constant but random, and the reference pitch serving as the reference of the pitch P of each prism portion is P ₀ , and the increase / decrease width of the reference pitch is [Delta] P, when the projection length of the light exit surface of the second inclined surface of a virtual reference prism portion pitch of the reference pitch P ₀ and d _0, pitch P of any of the prism portion, P = P ₀ Two conditions of + ΔP and 2d ₀ ≦ | ΔP | ≦ 5d ₀ It is an illuminating device characterized by being within a range that satisfies the formula.

§3.1. In this illuminating device, since the pitch of the prism portion of the light guide plate is random, the visibility of the illuminated object is reduced due to the striped ghost as described above (when the illuminated object is a display element, the display of the display element is reduced). It is possible to suppress deterioration of image visibility).

The light source of the illumination device is, for example, a cold cathode fluorescent tube, a hot cathode fluorescent tube, and an L including a plurality of linearly arranged LEDs.
A linear light source such as an ED array may be used. LED is the light source
And the like, and a conversion unit for converting the light emitted from the point light source into a linear light source.

The object (illumination object) illuminated by this illuminating device is not particularly limited, and may be, for example, a display element. More specifically, it may be a non-self-luminous display element such as a liquid crystal display element. Good. This illuminating device can be used as a front light of a reflective liquid crystal display element. This illuminating device may be used as a backlight of a transmissive or transflective liquid crystal display element. You may illuminate a display board, a printed matter, etc. with this illuminating device.

§4. Display Device The display device of the present invention has the above-mentioned illumination device and a display element facing the light exit surface of the light guide plate. That is, the display device of the present invention includes the above-mentioned light guide plate, the light source facing the light incident surface of the light guide plate, and the display element facing the light exit surface of the light guide plate.

In the display device, typically, the illumination device may be capable of illuminating the entire surface of the display area of the display element. That is, the light guide plate may typically have a size (area) that covers the entire display area of the display element.

The display element may be, for example, a reflective liquid crystal display element. The reflective liquid crystal display element has at least one liquid crystal layer, and may have a plurality of laminated liquid crystal layers. The reflective liquid crystal display element may be made flexible by employing, for example, a flexible resin substrate as the substrate holding the liquid crystal layer.

An air layer may be provided between the display element and the light guide plate. The display element and the light guide plate may be bonded with an adhesive having a lower refractive index than the light guide plate. For example, the display element and the light guide plate may be bonded in the non-display area of the display element.

In this display device, since the pitch of the prism portions of the light guide plate is random, it is possible to suppress the reduction in the visibility of the display image on the display element due to the stripe ghost as described above.

[0045] When the pixel pitch of the display elements and P _PX, the ratio of the reference pitch P ₀ and pixel pitch P _PX of prism portions of the light guide _{plate, 1.4 ≦ P 0 / P PX} ≦ 1.6 ( However, P ₀ / P _PX ≠ 1.5) (Equation 4) 2.4 ≦ P ₀ / P _PX ≦ 2.6 (where P ₀ / P _PX ≠ 2.5) (Equation 5) 1.4 ≦ P _PX / P ₀ ≦ 1.6 (however, P _PX / P ₀ ≠ 1.5) (Equation 6) 2.4 ≦ P _PX / P ₀ ≦ 2.6 (however, P _PX / P ₀ ≠ 2.5) (Equation 7) may be satisfied. By doing this, the pitch of the moire generated between the prism portion of the light guide plate and the pixel of the display element becomes small,
Moire is less visible. The display image of the display element is easier to see.

On the display element surface facing the light exit surface of the light guide plate,
Antireflection treatment may be applied. That is, an antireflection film may be provided on the surface of the display element facing the light guide plate. With this configuration, the reflection of light on the surface of the display element facing the light guide plate is suppressed, the brightness of the ghost light itself is reduced, and the ghost light itself is less visible. As a result, it is possible to further suppress the reduction in the visibility of the display image on the display element due to the ghost light. Antireflection treatment, for example, by applying an antireflection coating on the surface of the display element facing the light guide plate,
It may be performed by attaching an antireflection film.

The surface of the display element facing the light guide plate may be subjected to antiglare treatment. That is, an antiglare film may be provided on the surface of the display element facing the light guide plate. By doing so, the reflected light on the surface facing the light guide plate of the display element is scattered, and the contrast of the ghost light decreases,
The ghost light itself becomes more difficult to see. As a result, it is possible to further suppress the reduction in the visibility of the display image on the display element due to the ghost light. The antiglare treatment may be performed, for example, by applying an antiglare coating or pasting an antiglare film on the surface of the display element facing the light guide plate.

The items described in the description of the light guide plate, the illuminating device and the display element may be a combination of two or more.

[0049]

BEST MODE FOR CARRYING OUT THE INVENTION §5. Hereinafter, embodiments of the present invention will be described with reference to the drawings. A schematic perspective view and a schematic sectional view of an example of a reflective liquid crystal display device according to the present invention are shown in FIGS. 1 and 2, respectively.

The liquid crystal display device AP1 shown in FIGS. 1 and 2 includes a reflective liquid crystal display element LE1. The image displayed by the liquid crystal display device AP1 (liquid crystal display element LE1) is shown in FIG.
In, the display device AP1 is observed from above.

The liquid crystal display device AP1 further includes a lighting device LD1 including a light guide plate 3, a reflecting member 4 and a light source 5. This illuminating device LD1 is provided with a liquid crystal display element L so that the display can be observed even when there is little outside light (sunlight, indoor light, etc.), that is, the display can be observed even in a dark place.
It is for illuminating E1 from its front side.
The lighting device LD1 is a so-called front light. The light guide plate 3 of the illuminating device LD1 faces the front surface (observation side) of the liquid crystal display element LE1 (the upper side surface of the liquid crystal display element in FIG. 2).

The structure and the like of the liquid crystal display element LE1 will be described below, and then the illumination device (front light) LD1 will be described.
Will be described.

§5.1. A schematic sectional view and a schematic plan view of the liquid crystal display element LE1 are shown in FIGS. 3 and 4, respectively. In FIG. 3, the upper side of the liquid crystal display element LE1 is the observation side, that is, the side facing the light guide plate 3.

The liquid crystal display element LE1 includes a pair of substrates S1 and
It has S2 and a liquid crystal layer LCL arranged between these substrates. A black light absorbing film AB is formed on the back side of the substrate S2 arranged on the side opposite to the observation side.

The liquid crystal layer LCL is a liquid crystal (liquid crystal composition) LC.
Is a layer formed by. The liquid crystal LC is, in this example, a chiral nematic liquid crystal composition obtained by adding a chiral material to the nematic liquid crystal composition. The chiral nematic liquid crystal LC exhibits a cholesteric phase at room temperature. In this example, the chiral nematic liquid crystal LC has peaks of selective reflection wavelengths in two regions, a blue region and a yellow region. The selective reflection wavelength can be adjusted depending on the amount of the chiral material added to the nematic liquid crystal composition, the type of the chiral material, and the like.

A seal wall SW is formed around the liquid crystal layer LCL, and the seal wall SW is adhered to both the substrates S1 and S2. This prevents the liquid crystal LC from leaking from between the substrates.

The substrates S1 and S2 are both polyether sulfone (PES) films in this example, and have flexibility. As a result, the entire liquid crystal display element LE1 also has flexibility. Both the substrates S1 and S2 are transparent.

A column electrode E1, an insulating film IS1 and an alignment film O1 are formed in this order on the substrate S1. Similarly, on the other substrate S2, the row electrode E2, the insulating film IS2, and the alignment film O2 are formed in this order. The insulating film and the alignment film are not shown in FIG.

The column electrode E1 and the row electrode E2 are provided for simple matrix drive of the liquid crystal display element LE1 in this example. The column electrode E1 is composed of a plurality of strip electrodes E1b arranged in parallel at a predetermined pitch. Similarly, the row electrode E2 is composed of a plurality of strip electrodes E2b arranged in parallel with each other at a predetermined pitch. The width and pitch of the strip electrodes E1b of the column electrode E1 are the same as those of the strip electrode E2 of the row electrode E2.
It is the same as the width and pitch of 2b, respectively. The strip electrode E1b forming the column electrode E1 and the strip electrode E2b forming the row electrode E2 extend in directions orthogonal to each other, and these strip electrodes have a so-called matrix structure.

A plurality of spacers SP and a plurality of resin structures RS are arranged in the same layer as the liquid crystal layer LCL.
2 and 4, the spacer SP and the resin structure RS are not shown. The spacer SP is arranged between the substrates S1 and S2 in order to control the thickness of the liquid crystal layer LCL. The resin structure RS is adhered to both the alignment film O1 on the substrate S1 and the alignment film O2 on the substrate S2. As a result, the substrates S1 and S2 are adhered to each other. The resin structure RS suppresses widening of the inter-substrate gap (thickness of the liquid crystal layer) and also enhances the strength of the entire liquid crystal display element LE1.

The liquid crystal display element LE1 displays a reflection type image as follows. In this example, as shown in FIG. 4, a region where the strip-shaped electrode E1b of the column electrode and the strip-shaped electrode E2b of the row electrode E2 intersect and the peripheral region thereof are defined as one pixel P.
Image display is performed as X. Therefore, in this example, the pixel pitch P _PX is equal to the pitch of the strip electrodes E1b and E2b.

When a relatively high voltage is applied between the strip electrode E1b of the column electrode E1 and the strip electrode E2b of the row electrode E2, the chiral nematic liquid crystal LC of the pixel (pixel to be driven) corresponding to these strip electrodes is in the planar state. (Selective reflection state). As a result, the liquid crystal LC of the driving target pixel reflects the light of the selective reflection wavelength. In this example, since the liquid crystal LC has the peaks of the selective reflection wavelength in the two regions of the blue region and the yellow region as described above, when the liquid crystal LC of the driving target pixel is brought into the planar state, the pixel is white. (Blue + yellow) color is displayed.

When a relatively low voltage is applied between the strip electrodes E1b and E2b, the liquid crystal LC of the pixel to be driven becomes the focal conic state (transparent state). As a result, the color (black) of the light absorption film AB is displayed in the driven pixel.

When an intermediate voltage between the high voltage and the low voltage is applied between the strip electrodes E1b and E2b, the liquid crystal LC of the pixel to be driven is in a state in which the planar state and the focal conic state are mixed. As a result, in the pixel to be driven, an intermediate color is displayed according to the mixing ratio and the like.

The state of the liquid crystal LC is maintained even after the application of the voltage between the strip electrodes is stopped. That is, the liquid crystal display element LE1 using the chiral nematic liquid crystal LC
Has a memory property that can maintain the display content even if the voltage is not applied continuously.

As a result, the liquid crystal display element LE1 can display a desired image by applying a voltage according to the image information (image data) of the pixel between the strip electrodes corresponding to each pixel. .

§5.2. Thus, the liquid crystal display element LE1
The image display is performed by controlling reflection and transmission of light (sunlight, room light, etc.) incident on the liquid crystal layer LCL by the liquid crystal layer LCL. Therefore, when a sufficient amount of light does not enter the liquid crystal display element LE1, it becomes difficult to observe the display. In the liquid crystal display device AP1, the illumination device L including the light guide plate 3, the reflection member 4, and the light source 5 as described above so that the display can be observed even in a dark place.
D1 is provided (see FIGS. 1 and 2).

The light guide plate 3 faces the observation side surface (display surface) of the liquid crystal display element LE1. In order to illuminate the entire display area of the liquid crystal display element LE1, the light guide plate 3 faces the liquid crystal display element LE1 so as to cover this display area. Light guide plate 3
A gap is provided between the liquid crystal display element LE1 and the liquid crystal display element LE1. That is, an air layer is provided between the light guide plate 3 and the liquid crystal display element LE1. The light guide plate 3 and the liquid crystal display element LE1 are each supported by a supporting member (not shown). Instead of this, for example, the light guide plate 3 and the liquid crystal display element LE1 may be bonded with an adhesive in the non-display area.

The reflecting member 4 has a U-shaped cross section and has an opening 4a in a region facing the side end surface 31 of the light guide plate 3. The light source 5 is arranged inside the reflection member 4 and faces the side end surface 31 of the light guide plate 3 through the opening 4 a.

The light source 5 is a linear light source. In this example, the linear light guide body made of transparent resin is provided with an optical path changing means like the light guide plate, and LED arrays are arranged at both ends thereof. I am using one. LED by a drive device (not shown)
By applying a voltage to the array, the LED array (light source 5) emits light. The light source 5 may be, for example, a cold cathode tube instead of the LED array.

The inner surface of the reflecting member 4 surrounding the light source 5 is a reflecting surface having high light reflection efficiency. The light emitted from the light source 5 enters the inside of the light guide plate from the side end surface 31 of the light guide plate 3 directly or indirectly after being reflected by the inner surface of the reflecting member.
The side end surface 31 of the light guide plate is a light incident surface of the light guide plate.

The light guide plate 3 emits the light entering the light guide plate from the light incident surface 31 from the surface 33 facing the liquid crystal display element LE1 which is the object to be illuminated. Thereby, the liquid crystal display element L
E1 is illuminated. The light guide plate surface 33 from which light is emitted toward the liquid crystal display element that is the object to be illuminated is called a light emission surface. The light exit surface 33 is a flat surface in this example.

In the light guide plate 3, the light entering the light guide plate from the light incident surface 31 is emitted from the light emitting surface 33,
The surface 32 opposite to the light emitting surface 33 is a prism surface in order to uniformly emit light from each part of the light emitting surface 33.

The prism surface 32 includes a plurality of prism portions 32p.
Is included. The prism portions 32p are arranged side by side in the direction (X direction) from the side end surface 31 which is the light incident surface to the side end surface 34 on the opposite side.

Each prism portion 32p has a light incident surface 3
The first inclined surface 321 is arranged on the side closer to 1 (the side closer to the light source 5) and the second inclined surface 322 is arranged on the side farther from the light incident surface 31. Both the slopes 321 and 322 are inclined with respect to the light exit surface 33. The slopes 321 and 322 belonging to the same prism portion 32p are continuous,
A flat surface (a surface parallel to the light exit surface 33) between these slopes
There is no. In this example, each of the slopes 321 and 322 extends in a direction parallel to the direction in which the light incident surface 31 extends (Y direction).

The sloping surface 321 of each prism portion 32p mainly directs the light that directly or indirectly enters the sloping surface through the light incident surface 31 to the side end surface 34 opposite to the light incident surface (side end surface) 31. It is provided to guide in the direction (X direction). In the following description, the inclined surface 321 may be referred to as a light guide surface.

The slope 322 of each prism portion 32p
Is provided mainly for reflecting the light, which directly or indirectly enters the inclined surface through the light incident surface 31, toward the light emitting surface 33 and guides the light toward the light emitting surface 33. ing. In the following description, the slope 322 may be referred to as a reflecting surface.

As shown in FIG. 5, the light that has entered the light guide plate from the light incident surface 31 has a prism surface 32 and a light exit surface 33.
The light travels toward the side end surface 34 on the opposite side of the light exit surface (side end surface) 31 while being totally reflected. At this time, the light incident on the first inclined surface 321 of the prism surface 32 is totally reflected as described above, and travels toward the side end surface 34. On the other hand, the light incident on the second sloped surface 322 of the prism surface 32 is not reflected by the second sloped surface 32.
The light is reflected by the light emitting surface 33 toward the light emitting surface 33, and the light is irradiated from the light emitting surface 33 to the liquid crystal display element LE1 which is the illuminated object. In the direction from the light incident surface 31 to the side end surface 34 (X direction), the plurality of second inclined surfaces 32 are formed with a minute pitch.
Since 2 is provided, the light is emitted from the light emitting surface 33 substantially uniformly, and the liquid crystal display element LE1 which is the illuminated object can be illuminated substantially uniformly.

A reflective film may be formed on the side end face 34 in order to prevent light from leaking out of the light guide plate from the side end face 34. By doing so, the amount of illumination light can be increased.

§5.3. In the light guide plate 3, FIG.
As shown in (A) and the like, the pitch of each prism portion 32p is not constant but is set to a random value. In addition,
In FIG. 6A, the pitches of the prism portions 32p are P ₁ , P ₂ , P ₃ , ..., P _{K in} order from the light incident surface 31 side.

The pitch P of any prism portion 32p
_n (1 ≦ n ≦ K) is also within the range that satisfies the following expressions 8 and 9. P _n = P ₀ + ΔP (Equation 8) 2d ₀ ≦ | ΔP | ≦ 5d ₀ (Equation 9)

Here, P ₀ is a reference pitch that serves as a reference for the pitch P _n of each prism portion 32 p, and ΔP is an increase / decrease width of the reference pitch. Further, d ₀ is, as shown in FIG.
This is the projection length of the second inclined surface (reflection surface) 322 of the virtual reference prism portion 32p ₀ having the reference pitch P ₀ on the light exit surface 33.

This reference prism portion 32p₀The height of
H₀, The angle between the first slope 321 and the light exit surface 33
β₀, The angle between the second slope 322 and the light exit surface 33 is α₀
Then, d ₀= H₀/ Tan α₀= P₀tan β₀/
(Tan α₀+ Tan β₀). In addition, in the formula 9
D₀> 0 and ΔP ≠ 0.
Pitch P of the rhythm section 32_nAlso P_n≠ P₀Is. That is,
Pitch P on the prism surface 32₀Reference prism part 32p
₀Does not exist, and the pitch is the reference pitch P.₀Is the standard pre
The rhythm part is virtual.

According to the light guide plate 3, as shown in FIG.
A part of the light reflected by the second inclined surface (reflection surface) 322 and directed to the liquid crystal display element LE1 as the illumination light is reflected by the light exit surface 33 or the surface of the liquid crystal display element and travels toward the viewer side. It becomes a ghost light. Some of this ghost light is
The light is largely refracted or reflected by the second slope 322, and becomes light that does not reach the observer. As a result, the ghost light is perceived by the observer as a striped ghost (ghost stripes) in which dark lines and bright lines (bright lines) are lined up. The pitch of the dark lines of the striped ghost changes depending on the pitch of the prism portion of the light guide plate and the thickness of the light guide plate, and the number of dark lines that are visually observed depends on the elevation angle determined by the observation distance and the light guide distance on the observer side. Change.

If the pitch of the prism portions 32p is constant, a striped ghost in which dark lines are arranged at equal pitches occurs, and the striped ghost significantly obstructs the observation of the displayed image. On the other hand, in the light guide plate 3 described above, since the pitch of each prism portion 32p is random, the periodicity of the dark lines of the striped ghost disappears, and when the striped ghost in which dark lines of equal pitch are arranged is generated. In comparison, it is possible to suppress the reduction in the visibility of the display image due to the striped ghost. Since the width of the dark line increases in proportion to the area of the reflecting surface 322,
By making the pitch random on the basis of the projected length d ₀ of the reflecting surface 322, it is possible to reduce ghost more efficiently than when making the pitch random on the basis of the pitch.

§6. The pitch of the prism portions 32p of the light guide plate 3 may be changed as shown in FIGS. 7 (A) to 7 (C), for example. The angle between the second slope (reflection surface) 322 and the light emission surface 33 is α, the angle between the first slope (light guide surface) 321 and the light emission surface 33 is β, the first slope 321 and the second surface The angle between the slopes 322 is γ, and the height of the prism portion 32p is H. 7 (A), 7 (B) and 7 (C), the parameters α, β, γ, H whose values are changing.
Suffixes (subscripts) of “′” and “″” are attached to P and P.

For example, as shown in FIG. 7A, the height H and the angle α are kept constant and the angles β and γ are changed in any prism portion 32p to change the prism portion 3p.
The pitch P of 2p may be changed.

As shown in FIG. 7B, the angles α, β and γ are kept constant in any prism portion 32p and the height H is changed to change the pitch P of the prism portions 32p. Good.

As shown in FIG. 7C, the angle β and the height H are kept constant in any prism portion 32p, and the pitch P of the prism portion 32p is changed by changing the angles α and γ. Good.

In addition to this, for example, any prism portion 32
The height H may be fixed at p and the pitch P of the prism portion 32 may be changed by changing the angles α, β and γ.

Among the above, the angle α of FIG.
The method of changing the pitch by keeping β and γ constant and changing the height H has the following advantages.

The light guide plate 3 is manufactured, for example, by molding a resin such as an acrylic resin using a mold. The mold used for molding has an uneven surface corresponding to the prism surface 32. This mold is manufactured as follows. For example, as shown in FIGS. 8A to 8D, the die member 61 is cut by a cutting tool 62, and a linear groove 611 having a V-shaped cross section corresponding to each prism portion 32p is formed in the plurality of die members 61. By doing so, the mold is formed.

If the angle γ is constant, all the grooves 611 can be cut using the same cutting tool 62. The mold can be manufactured easily, efficiently and inexpensively. Therefore, the light guide plate 3 can be manufactured correspondingly at low cost.

Further, by merely controlling the feed distance x of the cutting tool 61 and the cutting depth z, an uneven surface corresponding to the prism surface 32 including prism portions having a desired random pitch can be formed on the mold member 61. it can. A mold can be manufactured that much more easily.

§7. The size of the prism portion 32p of the light guide plate 3 may be set to the following values, for example. Basically, the prism portion 32p of the light guide plate 3 is preferably inconspicuous so as not to hinder the observation of the display image by the liquid crystal display element LE1.

The reference pitch P ₀ may be set to about 0.2 mm or less because the critical pitch that can be visually recognized by human eyes is about 0.2 mm. The reference pitch P ₀ is 0.15 mm ≦ P
_The optimum _value is ₀ ≦ 0.20 mm.

The height H of the prism portion 32p is, for example, 1 μm.
It may be selected from the range satisfying m ≦ H ₀ ≦ 5 μm.

The angle α of the second inclined surface (reflection surface) 322 is in the range of 40 ° to 50 °, for example 45 °, in order to redirect the light incident on the inclined surface 322 toward the light exit surface 33.
It should be about.

The pitch P _n (= P _{0 of} each prism 32p)
+ ΔP) may be determined, for example, by generating the increase / decrease width ΔP of the reference pitch in the following procedure. Parameters of the reference prism part (P ₀ , α ₀ , H _0, etc.)
Then, d ₀ is calculated from the above, and 2d ₀ and 5d ₀ are determined. A sequence of numbers obtained by multiplying 5d ₀ by a random real number X between −1 and 1 is created, and a sequence smaller than 2d ₀ is excluded from the sequence. Here, the random real number X can be determined from X = 2 (R-1 / 2), where R is a random number from 0 to 1. If the increase / decrease width ΔP with respect to the reference pitch of each prism portion 32p is generated by the above procedure, ΔP is −5d.
₀ ~-2d _0, or becomes a random value in the range of + 2d ₀ ~ + 5d _0, the pitch P _n of each prism portion 32p,
It can be a random value within a predetermined range associated with the projection length of the reflection surface of the virtual reference prism portion. The light guide plate having the pitch thus determined is
It has been confirmed by optical simulation that the influence of the stripe ghost can be reduced when the height H of the prism portion 32p is up to 5 μm.

§8. An optical simulation of the striped ghost of the light guide plate was carried out and will be described below. An optical simulation was performed on the light guide plate A according to the present invention and the light guide plates B to D for comparison with the light guide plate A.
These light guide plates A to D are designed as follows.

(1) Light Guide Plate A In the light guide plate A, the pitch (= reference pitch) P ₀ of the reference prism portion (see FIG. 6B) is 200 μm, the angle α ₀ is 45 °, and the height H ₀ is H ₀ . The pitch of each prism portion 32p was designed to be 5 μm. In this case, d ₀ (= H ₀ /
tan α ₀ ) is 5 μm. When the variation width ΔP with respect to the reference pitch of each prism portion is generated using the above procedure, ΔP is −25 μm to −10 μm or +10 μm to +.
It takes a random value in the range of 25 μm. From the thus obtained ΔP, the pitch P _n of each prism portion of the light guide plate A was determined based on the equation 8 (P _n = P ₀ + ΔP). Similar to the light guide plate of FIG. 7B described above, the angle α (= 45 °), β and γ are constant in any prism portion, and the height H is changed to change the pitch of each prism portion. Was the random value determined above. The thickness of the light guide plate (the thickness from the bottom surface of the prism portion to the light exit surface) was 2.0 mm.
In the simulation, an acrylic resin having a refractive index n = 1.4914 was used as the material of the light guide plates A to D.

(2) Light guide plate B The pitch of each prism portion of the light guide plate B was fixed, and the pitch was set to the reference pitch P ₀ (= 200 μm) of the light guide plate A. Except for this, the light guide plate B was the same as the light guide plate A.

(3) Light Guide Plate C The light guide plate C was designed in the same manner as the light guide plate A, except that the pitch of the prism portions was random within the range of | ΔP | ≦ 5d ₀ .

(4) Light guide plate D The light guide plate D was designed in the same manner as the light guide plate A, except that the pitch of the prism portions was random within the range of | ΔP | ≦ 2d ₀ .

The optical simulation results of these light guide plates A to D are shown in FIG. From FIG. 15, the light guide plate A of the present invention is shown.
According to the above, it can be seen that the striped ghost can be suppressed as compared with the other light guide plates B to D.

It can be seen that in the light guide plate B, the contrast is periodically greatly reduced, and striped ghosts are generated. It can be seen that if the pitch of the prism portion is constant, a striped ghost with a large difference in contrast between the dark line portion and the bright line portion is generated.

Although the contrast of the light guide plate C is not as low as that of the light guide plate B, it is understood that the contrast is decreased at a cycle substantially corresponding to the light guide plate B and a striped ghost is generated. Comparing the light guide plates A and C,
It can be seen that the light guide plate A that does not include the prism portion having the pitch in this range can effectively suppress the striped ghost, as compared with the light guide plate C that includes the prism portion having the pitch of | ΔP | <2d ₀ . Note that 5d ₀ = 25 μm = 12.5
Because it is P _0/100, the pitch P _n of each prism portion of the light guide plate C _{is, P n = P 0 + ΔP} ( although, | ΔP | ≦ 1
It can also be thought of as 2.5P _0/100). Therefore, it can be seen that even if the pitch of each prism portion is random with a random degree of about 10% with respect to the reference pitch P ₀ as in the light guide plate C, the occurrence of striped ghost cannot be sufficiently reduced.

It is confirmed that in the light guide plate D, stripe ghosts equivalent to those in the light guide plate C are generated. It can be seen that even if the pitch of the prism portions is random, the stripe ghost cannot be sufficiently suppressed if the degree of randomness is small.

Further, two types of light guide plates having a constant pitch were actually manufactured and the visibility was confirmed. The prism portion is designed by adjusting the height of the reference prism portion of the light guide plate A described above for both light guide plates, and the light guide plate 1 has a pitch of 200 μm.
The light guide plate 2 has a constant pitch of 280 μm.
As a result, the unevenness of the prism portion was not conspicuous in the light guide plate 1 having a pitch of 200 μm, but the unevenness of the prism portion was clearly observed in the light guide plate 2 having a pitch of 280 μm,
When placed on the display element, it was confirmed that the visibility was clearly impaired as compared with the light guide plate 1.

§9. In the liquid crystal display device AP1 of FIG. 1 and the like, the moire fringes are formed by the light guide plate prism portions 32p having a random pattern but a parallel pattern and the pixels PX (see FIG. 4) of the liquid crystal display element having a grid pattern with an equal pitch. May occur. However, by setting the ratio between the reference pitch P ₀ of the light guide plate prism portion 32p and the pixel pitch P _PX within a predetermined range described below, it is possible to make the moire fringes less visible to the human eye.

Generally, a first pattern having a pitch P ₁ and
When the second pattern having the pitch P ₂ and the second pattern overlap each other at the angle θ, the pitch D _m of the moire fringes generated can be expressed by the following expression 11.

[Equation 1]

When θ = 0 ° (when the first pattern and the second pattern are parallel to each other), when the reference pitch is set to 1, and the moire fringe pitch D _m of the first to third orders is calculated from Equation 11, the pitch is The relationship between the ratio P ₁ / P ₂ and the moire fringe pitch D _m is as shown in FIG. The pitch of the n-order moire fringes calculated the P ₁ as P ₁ / n.

From FIG. 9, the pitch ratio (P ₁ / P ₂ ) is
It can be seen that in the vicinity of 1.5 and in the vicinity of 2.5, the pitches D _m of the first to third moire fringes become small.
When the pitch ratio (P ₁ / P ₂ ) is 1.5 or 2.5, moiré occurs when it reaches the lowest common multiple, which is not preferable.

When this result is applied to the liquid crystal display device AP1, the reference pitch P ₀ of the prism portion and the image pitch P
_1. The pitch ratio P ₀ / P _PX or P _PX / P ₀ with _PX is in the range of 1.4 to 1.6 excluding 1.5, or excluding 2.5.
When it is in the range of 4 to 2.6, the pitch D _{m of the} moire fringes can be made so small that it cannot be visually recognized by the human eye, and no moire fringes are generated at the position of the least common multiple.

That is, the pitch ratio P ₀ / P _PX or P _PX / P
₀ is expressed as 1.4 ≦ P ₀ / P _PX ≦ 1.6 (however, P ₀ / P _PX ≠ 1.5) 2.4 ≦ P ₀ / P _PX ≦ 2.6 (however, P ₀ / P _PX ≠ 2.5) 1.4 ≦ P _PX / P ₀ ≦ 1.6 (however, P _PX / P ₀ ≠ 1.5) 2.4 ≦ P _PX / P ₀ ≦ 2.6 (however P _PX / If any one of the four conditional expressions (P ₀ ≠ 2.5) is satisfied, the pitch of the moire fringes becomes so small that it cannot be recognized by human eyes, so that the visibility of the display image due to the moire fringes decreases. Can be suppressed.

For example, when the reference pitch P ₀ is 0.2 mm and the pixel pitch P _PX is 0.135 mm, P ₀ / P _PX becomes about 1.48. The pitch M of the first to third moire fringes generated at this time is about 0.4 mm or less, which is sufficiently small that it is hard to be visually recognized.

§10. A schematic cross-sectional view of another example of the reflective liquid crystal display device is shown in FIG. The reflective liquid crystal display device AP2 of FIG. 10 has the same structure as the reflective liquid crystal display device AP1 of FIG. 2 except as described below.

In the liquid crystal display device AP2, the light guide plate 3
An antireflection film 71 is formed on the light emitting surface 33. In this example, the antireflection film 71 is formed by applying an antireflection coating to the light emitting surface 33.

Further, in the liquid crystal display device AP2, the antireflection film 72 is formed on the surface of the liquid crystal display element LE1 facing the light guide plate 3. In this example, the antireflection film 72 is formed by attaching an antireflection film. The antireflection film 72 may be attached to the surface of the liquid crystal display element using, for example, a transparent adhesive sheet or a transparent adhesive.

The liquid crystal display device AP2 has the following advantages.
The antireflection films 71 and 72 can suppress the reflection on the light emitting surface 33 and the reflection on the surface of the liquid crystal display element, which is an object to be illuminated, which cause stripe ghosts. As a result, the ghost light is reduced, the contrast of the ghost stripes is reduced, and the ghost stripes themselves are less visible to the observer. Therefore, the display image by the liquid crystal display element LE1 can be satisfactorily observed.

The antireflection film 71 on the light emitting surface 33 of the light guide plate may be formed by attaching an antireflection film to the light emitting surface 33. Further, the antireflection film 72 on the surface of the liquid crystal display element LE1 which is the object to be illuminated may be formed by applying an antireflection coating. Further, instead of performing the antireflection treatment on both the light emitting surface of the light guide plate and the surface of the object to be illuminated, the antireflection treatment may be performed on only one of these surfaces.

An antiglare film (antiglare film) 73 may be provided in place of the antireflection film 72 on the surface of the liquid crystal display element LE1 to be illuminated, as in the liquid crystal display device AP3 of FIG. The antiglare film 73 is formed by attaching an antiglare film to the surface of the liquid crystal display element. Since the reflected light on the surface of the liquid crystal display element is diffused by the antiglare film 73, the ghost light directed to the viewer is reduced. As a result, as in the case of providing the antireflection film, the contrast of the ghost stripes is lowered, and the ghost stripes are less likely to be visually recognized by an observer. Therefore, the display image by the liquid crystal display element LE1 can be satisfactorily observed.

§8. As the liquid crystal display element in the reflective liquid crystal display device, a laminated liquid crystal display element having a plurality of liquid crystal layers is adopted instead of the liquid crystal display element (single-layer liquid crystal display element) LE1 having only one liquid crystal layer in FIG. You may.

FIG. 12 shows a schematic sectional view of an example of the multi-layer liquid crystal display element. The upper side in FIG. 12 is the observation side, that is, the side facing the light guide plate 3.

The multi-layer liquid crystal display element LE2 shown in FIG. 12 is formed by stacking three liquid crystal display cells LE2b, LE2g and LE2r. On the back side of the liquid crystal display cell LE2r arranged farthest from the observation side, a black light absorption film AB is provided.
Is provided.

Liquid crystal display cells LE2b, LE2g, LE2
r is for displaying blue, green and red respectively. Adjacent liquid crystal display cells are adhered to each other by an adhesive layer AD.

Each liquid crystal display cell LE2b, LE2g, LE
2r has the same structure as the liquid crystal display element LE1 of FIG. For example, a liquid crystal display cell LE2b for blue display
Has a substrate S1b and a substrate S2b, and a chiral nematic liquid crystal LCb is sandwiched between these substrates. An electrode E1, an insulating film IS1, and an alignment film O1 are formed in this order on the substrate S1b. An electrode E2, an insulating film IS2, and an alignment film O2 are formed in this order on the substrate S2b. The chiral nematic liquid crystal LCb is
It exhibits a cholesteric phase at room temperature and has a peak of selective reflection wavelength in the blue region.

The other liquid crystal display cells LE2g and LE2r also have the same structure as the liquid crystal display cell LE2b. However, in the liquid crystal display cell LE2g for green display, a chiral nematic liquid crystal LCg having a peak of selective reflection wavelength in the green region is arranged between the substrates.
Further, in the liquid crystal display cell LE2r for displaying red,
Chiral nematic liquid crystal LCr having a selective reflection wavelength peak in the red region is arranged between the substrates.

As described above, in the multilayer liquid crystal display element LE2, the liquid crystal layer for blue display formed of the liquid crystal LCb, the liquid crystal layer for green display formed of the liquid crystal LCg,
In addition, three liquid crystal layers for red display formed of the liquid crystal LCr are laminated.

The multi-layer liquid crystal display element LE2 including the liquid crystal layers for displaying blue, green and red enables color display.

§9. In a multi-layer liquid crystal display element, two substrates arranged between adjacent liquid crystal layers are made common,
It may be replaced with one substrate.

FIG. 13 shows a schematic cross-sectional view of an example of a multi-layer liquid crystal display element in which the substrates are commonly used.

The multi-layer liquid crystal display element LE3 shown in FIG. 13 is obtained by sharing two substrates arranged between adjacent liquid crystal layers in the multi-layer liquid crystal display element LE2 shown in FIG.
That is, in the display element LE3, the substrate SC1 is adopted as a common substrate in which the substrate S2b and the substrate S1g in the display element LE2 are shared. In addition, the display element L
The substrate SC2 is adopted as a common substrate in which the substrate S2g and the substrate S1r in E2 are made common.

On the surface of the common substrate SC1 facing the liquid crystal LCb, the functional film (electrode E) formed on the substrate S2b is formed.
2. The insulating film IS2 and the alignment film O2) are formed, and the functional film formed on the substrate S1g is formed on the surface facing the liquid crystal LCg. Similarly, the functional film formed on the substrate S2g is formed on the surface of the common substrate SC2 facing the liquid crystal LCg, and the functional film formed on the surface of the common substrate SC2 facing the liquid crystal LCr is formed on the substrate S1r. A functional film is formed.

By adopting such a common substrate, the multi-layer liquid crystal display element LE3 can be made thinner and lighter than the multi-layer liquid crystal display element LE2. Therefore, the reflective liquid crystal display device that employs the laminated liquid crystal display element LE3 can be made thinner and lighter than the reflective liquid crystal display element that employs the laminated liquid crystal display element LE2.

[0136]

As described above, the light guide plate according to the present invention can suppress the reduction in the visibility of the illuminated object due to the striped ghost.

Further, the illumination device according to the present invention can prevent the visibility of the illuminated object from being deteriorated due to the stripe ghost.

Further, the display device according to the present invention can suppress the reduction in the visibility of the display image of the display element due to the striped ghost, and the better display can be performed.

Further, the display device according to the present invention can suppress the generation of moire fringes due to the prism pattern of the light guide plate and the pixel pattern of the display element, and can perform a good display accordingly.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of an example of a reflective liquid crystal display device according to the present invention.

FIG. 2 is a schematic cross-sectional view of the reflective liquid crystal display device of FIG.

3 is a schematic cross-sectional view of a liquid crystal display element included in the reflective liquid crystal display device of FIG.

4 is a schematic plan view of the liquid crystal display element of FIG.

5 is a diagram showing an optical path of light in a light guide plate of the reflective liquid crystal display device of FIG.

FIG. 6 (A) is a diagram showing a pitch of prism portions of a light guide plate, and FIG. 6 (B) is a diagram showing a reference prism portion.

7A to 7C are diagrams showing a method of changing the pitch of the prism portions of the light guide plate.

FIG. 8A to FIG. 8D are diagrams showing a process of manufacturing a mold used when manufacturing the light guide plate.

FIG. 9 is a diagram showing the relationship between the pitch ratio of two periodic patterns and the pitch of moire fringes generated when these patterns are superposed.

FIG. 10 is a schematic cross-sectional view of another example of the reflective liquid crystal display device according to the present invention.

FIG. 11 is a schematic cross-sectional view of still another example of the reflective liquid crystal display device according to the present invention.

FIG. 12 is a schematic cross-sectional view of an example of a multi-layer liquid crystal display element.

FIG. 13 is a schematic cross-sectional view of another example of a multi-layer liquid crystal display element.

FIG. 14 is a diagram showing how a striped ghost occurs.

FIG. 15 is a diagram showing a situation in which a striped ghost is generated by an optical simulation.

[Explanation of symbols]

AP1 to AP3 reflective liquid crystal display device (display device) LE1 liquid crystal display elements LE2, LE3 laminated liquid crystal display element (liquid crystal display element) S1, S2, S1b, S2b, S1g, S2g, S1
r, S2r substrate SC1, SC2 common substrate E1, E2 electrodes IS1, IS2 insulating film O1, O2 alignment film LCL liquid crystal layer LC, LCb, LCg, LCr chiral nematic liquid crystal AB light absorption film SP spacer RS resin structure SW seal wall AD Adhesive layer 3 Light guide plate 31 Light incident surface (side end surface) 32 Prism surface 32p Prism section 321 First slope (light guide surface) of prism section 322 Second slope (reflection surface) of prism section 33 Light exit surface 34 Side end surface 4 Reflecting member 5 Light source 61 Mold member 62 Bites 71, 72 Antireflection film 73 Antiglare film

Continued front page    F-term (reference) 2H038 AA55 BA06                 2H042 CA13 CA17                 2H091 FA14X FA21X FA23X FA34Z                       FA37X FA45X FD22 HA11                       LA16

Claims (5)

[Claims] 1. A light guide plate comprising a light source, a light incident surface facing the light source, a prism surface including a plurality of prism portions, and a light exit surface opposite to the prism surface, the prism of the light guide plate. All of the prism parts of the surface,
The first slope is close to the light incident surface, and the second slope is far from the light incident surface. In any prism portion, the first slope and the second slope are continuous, and each prism The pitch of the portions is not constant but random, and the reference pitch serving as the reference of the pitch P of each prism portion is P ₀ , the increment / decrement width of the reference pitch is ΔP, and the pitch is the reference pitch P _0. When the projection length of the second inclined surface of each part on the light exit surface is d ₀ , the pitch P of any prism part is P = P ₀ + ΔP, and 2d ₀ ≦ | ΔP | ≦ 5d ₀ An illuminating device that is within a range that satisfies a conditional expression. 2. The first slope and the second slope of the prism portion of the light guide plate.
The illumination device according to claim 1, wherein the angle between the inclined surfaces is the same in any prism portion. 3. The lighting device according to claim 1, wherein the light exit surface of the light guide plate is subjected to antireflection treatment. 4. A display device comprising: the lighting device according to claim 1; and a display element facing a light exit surface of a light guide plate of the lighting device. 5. When the pixel pitch P _PX in the display device, the ratio of the reference pitch P ₀ and pixel pitch P _PX prism portion of the light guide _{plate, 1.4 ≦ P 0 / P PX} ≦ 1.6 (however, P ₀ / P _PX ≠
1.5), 2.4 ≦ P ₀ / P _PX ≦ 2.6 (where P ₀ / P _PX ≠
2.5), 1.4 ≦ P _PX / P ₀ ≦ 1.6 (where P _PX / P ₀ ≠
1.5), and 2.4 ≦ P _PX / P ₀ ≦ 2.6 (where P _PX / P ₀ ≠
2.5), The display device according to claim 4, which satisfies any one of the four conditional expressions.