CN100520552C - Brightness enhancement in tir-modulated electrophoretic reflective image displays - Google Patents

Abstract

A reflective display has a plurality of transparent hemi-beads (60), each hemi-bead (60) having a reflective area (80) surrounding a non-reflective area (82). Light-absorbing particles (26) are suspended therein and move toward or away from the hemi-beads (60), selectively inhibiting or promoting total internal reflection of light incident on the hemi-beads (60). By selectively reflecting light through the non-reflective region (82) of the hemibead (60), for example by forming a patterned electrode (48) using a conductive region (104) and a plurality of reflective regions (108); making the reflective region of the electrode ( 108) aligning with the non-reflective regions (82) of the hemibeads; and applying a voltage across the electrodes (48) across the medium (20) so that the particles (26) are substantially aligned with them at positions where they substantially cover the hemibeads (60) Electrophoretic movement is performed between another position covering the conductive region (104) of the electrode but not covering the reflective region (108) of the electrode to increase the reflectivity of the display.

Description

Brightness in the TIR-modulated electrophoretic reflected image display strengthens

The reference of related application

The U.S. Provisional Patent Application series number that the application requires to submit on April 15th, 2005 is no.60/671, the right of priority of 538 patented claim, and the U.S. Provisional Patent Application series number that requires to submit on January 17th, 2006 is no.60/759, the right of priority of 772 patented claim.

Technical field

The application is about being No.5 in the patent No., 999,307,6,064,784,6,215,920,6,865,011,6,885,496 and 6, the brightness of the reflected image display of type described in 891,658 the United States Patent (USP) (reflectiveimage display) strengthens, and all these patents are comprised in herein with way of reference.

Background technology

Figure 1A is illustrated in U.S. Patent No. 6,885, and 496 and 6,891, the part of prior art reflection (light promptly) electrophoresis frustrated total internal reflection (TIR, total internal reflection) modulation (modulated) display 10 of type described in 658.Display 10 comprises transparent outside plate 12, and this transparent outside plate 12 is by at (the η for example of the high index of refraction with smooth appearance surfaces 17 ₂〉～1.75) partly embed a large amount of highs index of refraction (η for example in the inside surface of polymeric material 16 ₁〉～1.90) transparent sphere or roughly spherical pearl 14 form, and wherein observer V observes smooth appearance surfaces 17 by the angular range of direction of observation Y." inwardly " and " outwards " direction is represented by double-headed arrow Z.Pearl 14 is tightly packaged together, thereby from becoming inwardly outstanding individual layer 18, the thickness of this individual layer 18 is substantially equal to the diameter of a pearl 14.Ideally, all pearls of each pearl 14 contact and this pearl direct neighbor.Between adjacent beads, keep minimum aperture gap (ideally, very close to each other).

By hold medium 20 in the reservoir 22 that is limited by lower plate 24, it is adjacent with the part of inwardly giving prominence to from material 16 of pearl 14 that electrophoretic medium 20 keeps.Inertia, low-refraction (promptly less than about 1.35), low-viscosity electrical isolation liquid be as can be from 3M, St.Paul, the Flourinert that MN obtains ^TMHydrocarbon liquid (the η of perfluorinate ₃～1.27) be suitable electrophoretic medium.Other liquid, or water also can be used as electrophoretic medium 20.Therefore form pearl: liquid TIR interface.Medium 20 contains the suspending liquid of the fine dispersion of scattered light and/or light absorbing particle 26, as pigment, by dyed or other scattered/absorbed silica or latex particle etc.The optical characteristics of plate 24 is inessential relatively: plate 24 need only be formed for holding the reservoir of electrophoretic medium 20 and particle 26, and is used as the support of bottom plate electrode 48.

As everyone knows, the TIR interface that has between the two media of different refractivity is characterised in that critical angle θ _cWith less than θ _cThe light that incides on this interface of angle be transmitted by this interface.With greater than θ _cThe angle light that incides this interface stand TIR at this interface.Because this provides the polarizers of big angle scope that TIR takes place, therefore preferred little critical angle at the TIR interface.

Not having under the situation of electrophoresis behavior, shown in the right side of the dotted line among Figure 1A 28, the major part of the light by plate 12 and pearl 14 is carried out TIR in the inboard of pearl 14.For example, incident ray 30,32 is by material 16 and pearl 14 refractions.These light are at pearl: liquid TIR stands twice or TIR more frequently at the interface, shown in the point under light 30 situations 34,36; With shown in the point 38,40 under the situation of light 32.Total then internal reflection light is returned by pearl 14 and material 16 refractions and is penetrated as light 42,44 respectively, has realized " white " outward appearance in each reflector space or pixel.

Can pass medium 20 through electrode 46,48 (shown in dotted line) and apply voltage, described electrode 46,48 for example can carry out vapour deposition by the outside surface to the inside protuberate part of pearl 14 and plate 24 and obtain.Electrode 46 is transparent and in fact very thin, so that make light at pearl: the interference minimum at liquid TIR interface.Bottom plate electrode 48 needs not to be transparent.If activate electrophoretic medium 20 between electrode 46,48, to apply voltage by excitation voltage source 50, shown in the left side of dotted line 28, move in the zone of evanescent wave strong relatively (promptly in 0.25 micron of the inside surface of inwardly outstanding pearl 14 or nearer) 26 electrophoresis of suspended particle.In when, electrophoresis taking place as mentioned above moving when, particle 26 scatterings or absorbing light, therefore by being modified in pearl virtually and possibly: the real part of liquid TIR effective refractive index at the interface assigns to restrain or modulation TIR.This is by shown in the light 52,54, light 53,54 is scattered and/or absorbs, because they are in unfertile land (～0.5 μ m) evanescent wave zone, at pearl: liquid TIR shines on the particle 26 at the interface, respectively shown in 56/58, be implemented in each TIR-thus and restrain " dark " outward appearance in non-reflection-absorption zone or the pixel.By excitation voltage source 50 suitably, particle 26 need only move to the outside in thin evanescent wave zone, so that recover pearl: and the TIR ability at liquid TIR interface, and each " dark " non-reflection-absorption zone or pixel transitions become " white " reflector space or pixel.

As mentioned above, the clean optical characteristics of outside plate 12 can be controlled through the voltage that electrode 46,48 puts on medium 20 by control.Can cut apart these electrodes,, form image thus so that pass the zone that separates of plate 12 or the electrophoresis activation of pixel control medium 20.

Fig. 2 represents the sectional view of the amplification of the inside semisphere of one of spheroidal bead 14 or " half pearl " part 60.Half pearl 60 has normalization radius r=1 and refractive index η ₁With the center C to half pearl 60 be radius distance a apart from the light 62 of vertical incidence (through material 16) to half pearl 60 being angle θ with respect to radius axle 66 ₁Meet with the inside surface of half pearl 60.In order to carry out this desirable in theory discussion, suppose that it (is η that material 16 has the refractive index identical with half pearl 60 ₁=η ₂), so light 62 enters half pearl 60 through materials 16 and does not reflect.Light 62 reflects on the inside surface of half pearl 60, and as light 64 with angle θ with respect to radius axle 66 ₂Enter electrophoretic medium 20.

Consider now incident ray 68, this incident ray with the center C distance of half pearl 60 $a_c=\frac{{\mathrm{\η}}_3}{{\mathrm{\η}}_1}$ Position vertical incidence (through material 16) to half pearl 60.The needed minimum angle of TIR promptly takes place with critical angle θ c (with respect to radius axle 70) in light 68, incides on the inside surface of half pearl 60.Thereby light 68 is as light 72 experiences total internal reflection, and light 72 incides the inside surface of half pearl 60 once more with critical angle θ c.Correspondingly, light 74 is as light 76 experiences total internal reflection, and light 76 is vertically through more than half pearls 60 and enter the embedded part of pearl 14 and enter material 16.Therefore light 68 reflects in the direction roughly opposite with incident ray 68 as light 76.

To the center C of half pearl 60 apart from a 〉=a _cThe place incide all light on half pearl 60 towards light source toward back reflective (but being accurate retroeflection); This means when light source from top by and during a little in the observer back, strengthened reflection, and reflected light has diffusion (diffuse) characteristic, this gives its white appearance, this wishes in reflective display applications.Fig. 3 A, 3B and 3C represent three in the reflective-mode of half pearl 60.These and other modes coexist is useful for each pattern separately is discussed still.

In Fig. 3 A, at distance a _c＜a＜a ₁Scope in the light of incident carry out twice TIR (2-TIR pattern) and reflection ray being the relative wide arc φ at center in the opposite direction with the side of incident ray ₁In disperse.In Fig. 3 B, at distance a ₁＜a＜a ₂Scope in the light of incident carry out three TIR (3-TIR pattern) and reflection ray being the relative narrow arc φ at center in the opposite direction with the side of incident ray ₂＜φ ₁In disperse.In Fig. 3 C, at distance a ₂＜a≤a ₃Scope in the light of incident carry out four TIR (4-TIR pattern) and reflection ray is being the narrower arc φ at center in the opposite direction with the side with incident ray ₃＜φ ₂In disperse.Therefore half pearl 60 has the characteristic of " half retro-reflection ", part diffuse reflection (diffuse reflection), the scattering outward appearance that display 10 is had be similar to paper.

When main light source is positioned at the observer back, to compare with paper, display 10 has high relatively apparent brightness in small angle range.This is shown among Figure 1B, and Figure 1B has represented wide range α that observer V can observation display 10 and the light source S angle beta with respect to the angle deviating of observer V.As long as β is not too big, display 10 keeps high surface brightness.When normal incident, the reflectivity R of half pearl 60 (promptly inciding the part that the light on half pearl 60 is reflected by TIR) is provided by following equation (1):

$R=1-{\left(\frac{{\mathrm{\η}}_3}{{\mathrm{\η}}_1}\right)}^2---\left(1\right)$

η wherein ₁Be the refractive index of half pearl 60, η ₃It is refractive index with the surperficial adjacent medium of half pearl 60 that TIR takes place.Therefore, if half pearl 60 by low-index material such as polycarbonate (η ₁～1.59) if formation and adjacent media are Fluorinert (η ₃～1.27), then reach about 36% reflectivity R, and if half pearl 60 by high refractive index nano compound substance (η ₁～1.92) form, then reach about 56% reflectivity.When light source S (Figure 1B) is positioned at observer's head back, then can further strengthen the apparent brightness of display 10 by means of above-mentioned half-retro-reflection characteristic.

Shown in Fig. 4 A-4G, the reflectivity of half pearl 60 remains in the wide region of incident angle, has therefore improved the wide angle of display 10 and has observed characteristic and apparent brightness.For example, Fig. 4 A represents from vertical incidence-promptly, from half pearl 60 that watches with respect to the incident angle of offset from vertical 0 degree.In this case, for a 〉=a _cThe part 80 of half pearl 60 occur as ring.Ring is expressed as white, corresponding to the zone of reflecting half pearl 60 of incident light by TIR, as mentioned above.This ring surrounds the annular region 82 that is expressed as the dark space, corresponding to the non-echo area of half pearl 60, absorbs incident light and do not carry out TIR in non-echo area.Fig. 4 B-4G represents from depart from half pearl 60 seen of viewing angles of 15 degree, 30 degree, 45 degree, 60 degree, 75 degree and 90 degree respectively with respect to vertical direction.Fig. 4 B-4G and Fig. 4 A have relatively confirmed for a 〉=a _cThe viewing area of reflecting part of half pearl 60 increase along with incident angle and just reduce gradually.Even in the angle of grazing incidence (for example Fig. 4 F) almost, the observer still sees the major part of reflecting part 80, the wide angle range of observation that keeps apperance brightness is provided therefore for display 10.

Reflectivity by will independent half pearl multiply by the packaging efficiency coefficient f of half pearl, can obtain the assessment of reflectivity of inside " half pearl " hemisphere array partly of each spheroidal bead 14 shown in corresponding Figure 1A.The calculating of the packaging efficiency coefficient f of the structure of compact package relates to the application that well known to a person skilled in the art direct geometric techniques.Suppose that pearl 14 all is a same size, six side's closest packing (HCP) structures shown in Fig. 5 produce packaging efficiency f ∝ π/(6tan30 °)～90.7%.

Although the HCP structure produces the high-bulk-density of hemisphere, promptly will half pearl be deposited in during rectangle is provided with, also not needing half pearl is same size.Stochastic distribution with non-homogeneous size half pearl in about 1-50 mu m range has about 80% bulk density, and has the optical appearance of the HCP setting that is substantially similar to same size half pearl.For some reflective display applications, being provided with of this stochastic distribution may be more suitable in manufacturing, and for this reason, the reflectivity of piling up the minimizing that causes owing to little density is acceptable.Yet for simplicity, the HCP that following explanation focuses on same size half pearl of Fig. 5 is provided with, and hypothesis adopts generation refractive index η ₁/ η ₃=1.5 material.These factors are not thought restriction the scope of the present disclosure.

Described as the front about Fig. 2, be apart from a＜a with center C to half pearl 60 _cThe major part that impinges perpendicularly on the light on the flat outer surface of half pearl 60 is not carried out TIR, therefore by 60 reflections of half pearl.Instead, the major part of this light is produced dark non-reflective circular region 82 (Fig. 4 A-4G) by 10 scatterings of prior art display and/or absorption on half pearl 60.Fig. 5 represents a plurality of so dark non-reflector spaces 82, and each dark non-reflector space 82 annular region 80 that is reflected is surrounded, as previously mentioned.

The average surface reflectance R of half pearl 60 is by the area of tore of reflection 80 and recently determining of the total area that comprises tore of reflection 80 and dark annular region 82.According to equation (1), this ratio is again by the refractive index η of half pearl 60 ₁Refractive index η with the medium on the surface that is adjacent to half pearl 60 that TIR takes place ₃Ratio determine.Therefore, be apparent that the refractive index η of average surface reflectance R along with half pearl 60 ₁Refractive index η with adjacent media ₃Ratio increase.For example, air (η ₃～1.0) the semisphere water droplet (η in ₁～1.33) average surface reflectance R is approximately 43%; Airborne glass hemisphere (η ₁～1.5) average surface reflectance R is approximately 55%; And adamas hemisphere (η ₁～2.4) average surface reflectance R surpasses 82%.

Although using the pearl of aforesaid sphere (or semisphere) shape to make display 10 is very easily, even spherical (or semisphere) pearl 14 as far as possible closely is deposited in together (Figure 1A) in individual layer 18, between adjacent beads, still keep intermediate space 84 (Fig. 5) inevitably.The light that incides on any gap 84 " is lost " sensuously, and they directly pass through electrophoretic medium 20, is observing the undesirable blackening point of generation on the surface 17.These spots are little of cannot see, and therefore can not damage the outward appearance of display 10, but they have damaged clean average surface reflectance (the net average surface reflectance) R that observes surface 17.

Above-mentioned " half-retro-reflection (semi-retro-reflective) " characteristic is very important in reflective display because light source S be positioned at observer V above and under the typical observation condition at rear portion, catoptrical major part is returned towards observer V.This produces because " half-retro-reflective enhancement factor " exceedance $R=1-{\left(\frac{{\mathrm{\η}}_3}{{\mathrm{\η}}_1}\right)}^2$ About 1.5 outward appearance reflectivity (apparent reflectance) (referring to " A HighReflectance; Wide Viewing Angle Reflective Display Using Total InternalReflection in Micro-Hemispheres; " Mossman, M.A. wait the people, Society forInformation Display, 23 ^RdInternational Display Research Conference, pages233-236, September15-18,2003, Phoenix, AZ).For example, at refractive index η ₁/ η ₃In=1.5 the system, 55% the average surface reflectance R that determines according to equation (1) is enhanced about 85% under above-mentioned half-retro-reflection type observation condition.

Independent half pearl 60 may diminish to and cannot see, and diameter is in the 2-50 mu m range, and as shown in Figure 5, they can be assembled into array, thereby produces because the display surface small, adjacent in a large number, that high reflection appears in reflective circular region 80.In these zones 80, TIR takes place, when particle 26 not with pearl 14 inside, when hemispherical portion contacts, they do not hinder reflection of incident light at (Figure 1A).Yet, in zone 82 and 84, TIR does not take place, move to the evanescent wave region exterior even particle 26 may absorb incident ray-particle 26, thereby they do not contact with inside, the hemispherical portion optics of pearl 14.For the size that increases each reflective circular region 80 with reduce this absorption loss thus, can increase refractive index ratio ₁/ η ₃ Non-reflector space 82,84 reduces the total surface reflectivity R of display 10 cumulatively.Because display 10 is reflective display, therefore wish this minimizing is minimized.

Ignore above-mentioned half-retro-reflective enhancement factor, have refractive index ratio ₁/ η ₃=1.5 system has 55% average surface reflectance R, as previously mentioned.Suppose that aforementioned packaging efficiency that HCP is provided with is about 91%, the overall average surface reflectivity of this system be 55% 91% or about 50%, this is hinting about 50% loss.41% of this loss is because the light absorption in the annular non-reflector space 82 causes; 9% of this loss is because the light absorption in the middle non-reflection gap 84 causes.Have refractive index value, the optical microstructure of special selection or be positioned at the outside of individual layer 18 (Figure 1A) or the material of the patterned surface on the inboard (patterned surface) reduces this absorption loss by use, can improve the reflectivity of display 10.

For example, because the maximum surface reflectivity of display 10 is determined by the refractive index value of half pearl 60 and electrophoretic medium 20, therefore by replacing testing low-refractivity liquid (refractive index is less than 1.35) can improve reflectivity with air (reflectivity=1.0) as electrophoretic medium.

Can improve the surface reflectivity of display 10, as described below, the outward appearance of improvement display.

The previous example of correlation technique and relative restriction be intended to make an explanation the explanation and nonrestrictive.Can make other restriction of correlation technique more obvious by reading instructions and learning accompanying drawing to those skilled in the art.

Description of drawings

During exemplary embodiments is shown in reference to the accompanying drawings.It is illustrative and nonrestrictive that embodiment disclosed herein and accompanying drawing are considered to.

Figure 1A is the disproportional enlarged drawing of fragment cross sectional side view that electrophoresis was subjected to or modulated the part of (modulated) prior art reflection-type image display.

Figure 1B schematically shows the wide angle range of observation α of Figure 1A display and the angular range beta of light source.

Fig. 2 is the amplification profile side view of semisphere (" half the pearl ") part of one of spheroidal bead of Figure 1A device.

Fig. 3 A, 3B and 3C represent to impinge perpendicularly on the deviation distance that increases by half-retro-reflection of the light on Fig. 2 half pearl, and wherein the deviation distance incident ray in this increase carries out respectively twice, three times and four TIR.

Fig. 4 A, 4B, 4C, 4D, 4E, 4F and 4G represent half pearl 60 seen with respect to the viewing angles of offset from vertical 0 degree, 15 degree, 30 degree, 45 degree, 60 degree, 75 degree and 90 degree from respectively.

Fig. 5 is the vertical view (being that the viewing angle of 0 degree is seen from offset from perpendicular promptly) of sectional view of the part of Fig. 1 display, and the spheroidal bead of six side's closest packing (HCP) structures is arranged in expression.

Fig. 6 A and 6B are the vertical views of the up-sizing of two optional backplane electrode patterns (pattern) of using with Fig. 5 structure.

Fig. 7 A and 7B are the cut-away section side views of the up-sizing of the part that is subjected to press down (i.e. modulation) reflection-type image display of the electrophoresis in conjunction with Fig. 6 A backplane electrode patterns.

Fig. 8 is that what to be combined that electrophoresis suspend to absorb and the electrophoresis of reflection grain is subjected to or to modulate the reflection-type image display is not the sectional view that amplifies in proportion.

Fig. 9 be combine the reflection porous membrane electrophoresis be subjected to or modulate the reflection-type image display a part be not the sectional view that amplifies in proportion.

Figure 10 be the electrophoresis that combines extra polymeric material in the gap between adjacent half pearl be subjected to or modulate the reflection-type image display a part be not the sectional view that amplifies in proportion.

Embodiment

In order to be more conducive to those skilled in the art's understanding, introduce concrete details below.Yet, unnecessary smudgy and do not illustrate or introduce known elements for fear of bringing to the disclosure.Correspondingly, following explanation and accompanying drawing are illustrative and not restrictive.

Can use among Fig. 6 A or the 6B one of the figure 100 described respectively or 102 on plate 24, to form bottom plate electrode 48.Black region the 104, the 106th, conductive region, and can be reflectivity or non-reflexive.White portion the 108,110, the 112nd, reflector space, and can be conduction or non-conductive-as long as non-conductive between zone 108,110 and 112 and regional 104,106.

Reflector space 108,110 preferably is respectively round-shaped, and radius is more than or equal to the radius of one of non-reflection border circular areas 82 of one of (preferably equaling) half pearl 60.The overall dimension in the zone 104 of pattern 100 and shape are substantially similar to the overall dimension and the shape in the zone 80,84 of half pearl 60.

The optical property in zone 104,106 is inessential relatively, and is the same with the optical property of plate 24.Yet, cremasteric reflex outside surface and regional 104 (or 106) of formation thereon on plate 24, and 108 (or 110,112), the remainder of the reflective outer surface of plate 24 formation zone, this is favourable.

When using as described as follows, patterning (patterned) bottom plate electrode 100 has reduced because the absorption loss that the light absorption in zone 82 causes does not still reduce because the absorption loss that the light absorption in the gap area 84 causes.On the contrary, when using as described as follows, patterned backplane electrode 102 has reduced because the absorption loss that the light absorption in the zone 82 and 84 causes.This realizes by making figure 102 be formed with each reflector space 112, wherein the size and dimension of each reflector space 112 is substantially similar to the size and dimension in one of gap 84, each zone 112 with respect to its adjacent reflector space 110 be positioned at with respect on the identical position, the position in the corresponding gap 84 of the adjacent area 82 in that gap.

Patterned backplane electrode 100 (or 102) is provided with respect to individual layer 18, thereby each circular reflector space 108 (or 110) is aimed at a corresponding non-reflection border circular areas 82; Conductive region 104 (or 106) is aimed at reflector space 80.

When activating electrophoretic medium 20 by excitation voltage source 50 to apply voltage between electrode 46 and 48, particle 26 covers the inside surface of half pearl 60 of individual layer 18 basically, shown in Fig. 7 A (Fig. 7 A represents to utilize the non-reflective state of patterned backplane electrode 100).Particle 26 is absorbed into the light (for example light 114) that is mapped on the reflective circular region 80 by aforesaid inhibition or modulation TIR, and absorbs the light (for example light 116) that does not carry out TIR and otherwise pass through pearl 14.Particle 26 needn't cover the inside surface of half pearl 60 fully, because introduce with reference to Fig. 2 as the front, a lot of incident raies and half pearl are harmonious for more than 60 time, thereby the essence coverage rate causes the acceptable level that absorbs.

In the reflective condition shown in Fig. 7 B, particle 26 is adsorbed to the conductive region 104 conductive region 106 of patterned backplane electrode 102 (or be adsorbed onto) of patterned backplane electrode 100.Aim at reflective circular region 80 owing to regional 104, so particle 26 be cannot see (that is, owing to the light 114 that otherwise shines particle 26 is reflected by zone 80) from viewing angle.Without undergoing TIR but shine on one of reflector space 108, therefore also be reflected through the light 116 of more than half pearls 60 transmission.

If half pearl individual layer 18 is positioned at the suitable distance of reflector space 108 tops, the light toward reflective annular regions 80 that then is transmitted focuses on, and makes these light roughly return on the direction that they come.This has further strengthened the plate-retro-reflection characteristic of display, and can cause surpassing 100% the reflectance value of feeling.Even utilization and the relevant absorption loss of R-G-B (RGB) color filter array, patterned backplane electrode 100,102 is convenient to make the reflected image display with the brightness that can compare with the brightness of color ink on the blank sheet of paper.

Fig. 8 represents another kind of display brightness (being reflectivity) enhancement techniques, has wherein mixed absorbing particles 26 in electrophoretic medium 20, and has utilized the suspending liquid of the fine dispersion of reflective beads or particle 118.The mean diameter of reflective beads 118 is basically than the mean diameter of absorbing particles 26 big (for example, being about 10 times).Reflective beads 118 can be static neutrality (electrostatically neutral), thus the electric field effects that they will not applied.Perhaps, reflective beads 118 can have the electrostatic charge opposite with absorbing particles 26, makes that pearl 118 will be from particle 26 in opposite direction motion when standing to apply electric field.Although as the stable suspension that keeps opposite charged particle is reverse intuition, but this can realize (referring to Amundson by using suitable stabilization suspension dispersive agent, K., Deng the people, " Microencapsulated Electrophoretic Materials for Electronic PaperDisplays; " Society for Information Display, 20 ^ThInternational Display ResearchConference Proceeding, pages 84-87,25-28 day in September, 2000, Palm Beach, FL).Reflective beads 118 can be to have any granular material that reflects (for example white) basically that suitable particle size distributes, although high-index material such as titania (η～2.4) are preferred.

Do not having under the situation of electrophoresis behavior, shown in the left side of the dotted line 28 of Fig. 8, less absorbing particles 26 is tending towards towards lower plate 24, setting below bigger reflective beads 118.Therefore increase reflectivity, this is because the incident ray (for example light 120) that is otherwise absorbed by non-reflection border circular areas 82 has been reflected (for example light 122) by pearl 118.Aforesaid total internal reflection (for example light 126) takes place in the light (for example light 124) that incides on the reflective circular region 80.

When voltage put on medium 20, shown in 28 right sides of the dotted line among Fig. 8, the gap electrophoresis of less absorbing particles 26 between pearl 118 moved to the inside surface of half pearl 60.When so moving to this absorbing state, particle 26 is absorbed into the light (for example light 128) that is mapped on the reflective circular region 80 by aforesaid supression or modulation TIR, and absorbs the light (for example light 130) that does not carry out TIR but otherwise pass through pearl 14.Correspondingly, reflective beads 118 forms porous filter, allows absorbing particles 26 outwards to move, thereby contacts with half pearl 60 that is in absorbing state; And move inward from half pearl 60 that is in reflective condition, consider from the angle of direct-view thus, absorbing particles 26 is fogged at reflective condition.Represented spherical reflective beads 118 although it will be appreciated by those skilled in the art that Fig. 8, this shape is not that main-pearl 118 can be an arbitrary shape.

Except brightness strengthened, Fig. 8 technology also provided other advantage.For example, if reflective beads 118 with sufficiently high density setting, then their long term lateral of being tending towards hindering absorbing particles 26 move, and therefore make the gathering of absorbing particles 26 slack-off.This gathering may cause the image degradation of electrophoretic image display.

Can assess through the attainable brightness enhancing of Fig. 8 technology (being reflectivity).For example, if hypothesis reflective beads 118 has about 40% diffuse reflectance, and if also suppose the whole of the aforesaid 50% absorption loss zone of reflective beads 118 influences, realize that then the brightness of about 20% (that is, 50% of 40%) strengthens.

Fig. 9 represents another optional display brightness (being reflectivity) enhancement techniques, wherein reflects between the inside surface and lower plate 24 that porous membrane 140 is arranged on half pearl 60.The mean diameter of the aperture in the film 140 is basically than the mean diameter of absorbing particles 26 big (for example, being about 10 times).Aperture in the film 140 constitutes the enough big part (for example at least 20%) of the total surface area of film 140, thereby allows absorbing particles 26 to pass through film 140 substantially in the clear.Film 140 can be made of porous film material such as polycarbonate or fibrage film.The outside surface 142 of film 140 is high reflection, and can be scattering or direct reflection.Suitable reflective film 140 can be by inborn reflex material such as multilayer broadband reflection device (for example can be from 3M, St.Paul, the multi-layer optical film that MN obtains) or calorize Mylar ^TMFlexible membrane forms, and perhaps applies outside surface 142 by use standard vapor deposition techniques with reflection (for example aluminium) film and forms.

Under the situation that does not have electrophoresis behavior, shown in the left side of the dotted line among Fig. 9 28, less absorbing particles 26 be tending towards by film 140 aperture, be provided with towards lower plate 24.Therefore increase reflectivity, this is because the incident ray (for example light 144) that is additionally absorbed by non-reflection border circular areas 82 has been reflected (for example light 146) by the reflective outer surface 142 of film 140.Aforesaid total internal reflection (for example light 150) takes place in the light (for example light 148) that incides on the reflective circular region 80.

When voltage put on medium 20, shown in 28 right sides of the dotted line among Fig. 9, absorbing particles 26 moved to the inside surface of half pearl 60 through the hole of film 140 electrophoresis.When so moving to this absorbing state, particle 26 is absorbed into the light (for example light 152) that is mapped on the reflective circular region 80 by aforesaid inhibition or modulation TIR, and absorption is not carried out TIR but the light (for example light 154) of process pearl 14.The hole of film 140 allows absorbing particles 26 outwards to move, thereby contacts with half pearl 60 that is in absorbing state; And move inward from half pearl 60 that is in reflective condition, consider from the angle of direct-view thus, absorbing particles 26 is fogged at reflective condition.

Can assess through the attainable brightness enhancing of Fig. 9 technology (being reflectivity).For example, if the outside surface 142 of hypothesis film 140 has about 60% total reflectivity, and the aforesaid 50% absorption loss zone of hypothesis influence is whole, then realizes the brightness enhancing of about 30% (promptly 60% 50%).

Figure 10 represents another optional display brightness (being reflectivity) enhancement techniques, has wherein revised the void area 160 of the outside plate 12 between half pearl 60, thereby has increased reflectivity.Thereby this is to use the reflective polymer material that forms plates 12 so that roughly hemispheric shape is inwardly outstanding through void area 160 by partly embed spheroidal bead 14 in outside plate 12, and is between the half pearl part 60 of spheroidal bead 14, as shown in 162.

If each reflection polymer architecture 162 has " perfectly " hemispherical shape (theoretical ideal, still can not reach in practice), then the reflection of the light of polymer architecture 162 will be identical with the characteristic of aforesaid half pearl 60 with absorption characteristic.Although polymer architecture 162 is semisphere preferably, so that realize desirable reflectivity Characteristics, they need not to be perfect semisphere.Polymer architecture 162 need only be a semisphere roughly, and wherein their inside surface should have sufficiently high curvature to cause the TIR of incident ray.Can utilize with the front by absorbing particles 26 and be suppressed at the TIR that takes place in the polymer architecture 162 about the identical mode of half pearl, 60 described modes.

TIR can not take place in void area 160 usually, has therefore reduced the total reflectivity of plate 12.If half pearl 60 has six side's closest packing settings, then their overall average surface reflectivity is 91%, and as mentioned above, all the other 9% are owing to the light absorption in the void area 160 is lost.By being convenient in void area 160 TIR to take place, Figure 10 represents that the brightness enhancement techniques reduces this loss of 9% by nominal increase to 100% number percent that approaches plate 12, and wherein plate 12 has useful light reflection structure.

Replacement part in outside plate 12 is buried spheroidal bead 14, can improve brightness by the minimized in size that makes void area 160.For example, by adopting polymeric material as having plastic deformation characteristic's polycarbonate, so that non-curing or softening resin material form hemispherical dome structure inherently, people can be used as single integral array and make half pearl 60 and polymer architecture, needing to avoid the high precision mold.

The brightness enhancement techniques of Figure 10 can be used in combination with Fig. 7 A-7B, 8 or 9 brightness enhancement techniques, thereby further improves display brightness.

The front by the agency of a large amount of exemplary arrangement and embodiment, those skilled in the art will recognize that some modification, displacement, interpolation and its sub-portfolio.The claim of therefore enclosing claim below and introducing later is intended to be interpreted into and comprises this modification, displacement, interpolation and the sub-portfolio that falls in their true spirits and the scope.

Claims (47)

1. A reflective display, comprising: (a) a plurality of transparent semi-beads (60) protruding inwardly from the inner surface of the transparent plate (12) having the outer viewing surface (17), each semi-bead (60) having a reflection_area(80); (b) a second plate (24) spaced internally from said transparent plate (12) to define a reservoir between said transparent plate (12) and said second plate (24); (c) electrophoretic medium (20) within said reservoir; (d) a plurality of light absorbing particles (26) suspended in said medium; and (e) means for selectively reflecting light from said second plate (24) through said non-reflective region (82) of said hemibead (60). 2. A reflective display according to claim 1, said means for selectively reflecting light further comprising electrodes ( 48), said pattern (100 or 102) comprising: (i) a conductive region (104 or 106); and (b) a first plurality of reflective regions (108 or 110); Each of said first plurality of reflective regions (108 or 110) of said second plate (24) corresponds to and aligns with a corresponding one of said non-reflective regions (82) of said hemibead (60) . 3. The reflective display of claim 2, wherein each of said first plurality of reflective regions (108 or 110) of said second plate (24) is similar in size and shape to said half-beads The size and shape of said respective one of said non-reflective regions (82) of (60). 4. The reflective display of claim 3, wherein the overall size and shape of the conductive regions (104 and 106) are similar to the overall size and shape of the reflective region (80) of the hemibead (60) . 5. The reflective display of claim 4, wherein: Each of the semi-beads (60) is adjacent to another one or more of the semi-beads (60), and the display further includes one or more of the semi-beads (60) adjacent to each other. ) between non-reflective gaps (84); The pattern (100 or 102) further includes a second plurality of reflective regions (112) on said outer side of said second plate (24); and Each of the second plurality of reflective regions (112) corresponds to and is aligned with a respective one of the gaps (84). 6. The reflective display of claim 5, wherein each of the second plurality of reflective regions (112) is similar in size and shape to a corresponding one of the gaps (84). 7. The reflective display of claim 4, wherein: each of said non-reflective regions (82) of said hemibeads (60) has a circular shape, said circular shape having a first diameter; and Each of the first plurality of reflective regions (108 or 110) of the pattern (100 or 102) has a circular shape with a second diameter equal to the first diameter. 8. The reflective display according to claim 7, wherein each of said reflective regions (80) of said half-beads (60) has a ring shape. 9. The reflective display of claim 1, wherein said means for selectively reflecting light further comprises a plurality of reflective particles (118) suspended in said medium (20). 10. A reflective display according to claim 9, wherein the mean diameter of the reflective particles (118) is larger than the mean diameter of the absorbing particles (26). 11. A reflective display according to claim 10, wherein the mean diameter of the reflective particles (118) is 10 times the mean diameter of the absorbing particles (26). 12. The reflective display of claim 10, wherein the reflective particles (118) are electrostatically neutral. 13. The reflective display of claim 10, wherein the reflective particles (118) have an electrostatic charge opposite to the electrostatic charge of the absorbing particles (26). 14. The reflective display of claim 10, wherein the reflective particles (118) are white particles. 15. The reflective display of claim 10, wherein the reflective particles (118) are titanium dioxide particles. 16. The reflective display of claim 1, said means for selectively reflecting light further comprising a reflective, porous film (140). 17. A reflective display according to claim 16, wherein said film (140) further comprises pores, said pores having an average diameter greater than the average diameter of said absorbing particles (26). 18. A reflective display according to claim 17, wherein the average diameter of the pores is 10 times the average diameter of the absorbing particles (26). 19. A reflective display according to claim 17, wherein said film (140) has a surface area, said pores comprising a large fraction of said surface area so as to allow said absorbing particles (26) to pass unimpeded through the membrane (140). 20. The reflective display of claim 16, wherein the film (140) further comprises a diffusely reflective outer surface (142). 21. The reflective display of claim 16, wherein the film (140) further comprises a specularly reflective outer surface (142). 22. The reflective display according to claim 1, wherein each of said hemi-beads (60) is adjacent to another one or more of said hemi-beads (60) for selectively directing light The reflective means also includes a reflective structure (162) between each adjacent one or more hemibeads (60). 23. The reflective display according to claim 22, wherein each of said reflective structures (162) protrudes inwardly from said inner surface of said transparent plate (16). 24. A reflective display according to claim 23, wherein each of said reflective structures (162) has a hemispherical shape. 25. A reflective display according to claim 23, wherein each of said reflective structures (162) has a high curvature such that most of the light incident on said reflective structures (162) undergoes total internal reflection . 26. A method of increasing the reflectivity of a reflective display having: a plurality of transparent hemi-beads (60) viewed from a transparent plate (16) having an external viewing surface (17) ) protrudes inwardly, each hemisphere (60) has a reflective area (80) surrounding a non-reflective area (82); a second plate (24), spaced internally from said transparent plate (16), Thereby defining a reservoir between said transparent plate (16) and said second plate (24); an electrophoretic medium (20) within said reservoir; and a plurality of A light absorbing particle (26), said method comprising selectively reflecting light through said non-reflective region (82) of said hemibead (60). 27. The method of claim 26, wherein selectively reflecting light through said non-reflective regions of said hemibead (60) further comprises: An electrode (48) is formed on an outer side of the second plate (24) in a pattern (100 or 102), the pattern (100 or 102) comprising: (i) a non-reflective area (104 or 106); (ii) a first plurality of reflective regions (108 or 110); aligning each of said first plurality of reflective regions (108 or 110) with a corresponding one of said non-reflective regions (82) of said hemibead (60); and applying a voltage to the medium (20) to cause selective electrophoretic movement of the absorbent particles (26) between a first position and a second position, wherein in the first position the absorbent particles (26) covering the inner surface of said hemibead (60), in said second position said absorbing particles (26) covering said non-reflective area (104 or 106) of said electrode (48) without Covering the first plurality of reflective areas (108 or 110). 28. The method of claim 27, further comprising separating said transparent plate (12) from said second plate (24) by a distance selected such that said Incident light rays reflected by one of the first plurality of reflective regions (108 or 110) are reflected in a direction opposite to the direction of incidence of the incident light rays. 29. The method of claim 27, further comprising forming each of said first plurality of reflective regions (108 or 110) to be similar in size and shape to said non-reflective The size and shape of one of the regions (82). 30. The method of claim 27, further comprising forming said non-reflective area (104 or 106) to have an overall size and shape similar to the overall size and shape of said reflective area (80) of said half bead (60). size and shape. 31. The method of claim 30, wherein: each of said half-beads (60) is adjacent to another one or more of said half-beads (60); non-reflective gaps (84) exist between each adjacent one or more of said hemibeads (60); The pattern also includes a second plurality of reflective regions (112), each of the second plurality of reflective regions (112) having a size and shape similar to that of one of the gaps (84). 32. The method of claim 30, wherein each of said non-reflective regions (82) of said hemibeads (60) has a circular shape, said circular shape having a first diameter, said method Also comprising forming each of the first plurality of reflective regions (108 or 110) to have a circular shape with a second diameter equal to the first diameter. 33. The method of claim 26, wherein selectively reflecting said light through said non-reflective region (82) of said hemibead (60) further comprises: suspending a plurality of reflective particles (118) in said medium (20); Applying a voltage across the medium (20) causes selective electrophoretic movement of the absorbing particles (26) via the reflective particles (118) between a first position and a second position, wherein in the first In the first position, the absorbing particles (26) cover the inner surface of the hemi-beads (60), in the second position, the reflective particles (118) are located between the hemi-beads (60) and the absorbing particles (26). 34. The method of claim 33, wherein the mean diameter of the reflective particles (118) is larger than the mean diameter of the absorbing particles (26). 35. The method according to claim 34, wherein the mean diameter of the reflective particles (118) is 10 times the mean diameter of the absorbing particles (26). 36. The method of claim 33, further comprising electrostatically neutrally charging the reflective particles (118). 37. The method of claim 33, further comprising charging the reflective particles (118) with an electrostatic charge opposite to the electrostatic charge of the absorbing particles (26). 38. The method of claim 26, wherein selectively reflecting light through the non-reflective region (82) of the hemibead (60) further comprises: providing a reflective, porous film (140) in said medium (20) between said hemibeads (60) and said second plate (24); Applying a voltage across the medium (20) causes selective electrophoretic movement of the absorbing particles (26) through the membrane (140) between a first position and a second position, wherein in the first position At the position, the absorbent particles (26) cover the inner surface of the semi-beads (60), at the second position, the film (140) is located between the semi-beads (60) and the absorbent particles (26) between. 39. The method according to claim 38, wherein said membrane (140) further comprises pores having an average diameter greater than the average diameter of said absorbent particles (26). 40. A method according to claim 39, wherein the average diameter of the pores is 10 times the average diameter of the absorbent particles (26). 41. The method according to claim 38, wherein said membrane (140) has a surface area, said pores comprising a large fraction of said surface area so as to allow said absorbent particles (26) to pass unhindered through said The above film (140). 42. The method of claim 26, wherein: each of said half-beads (60) is adjacent to another one or more of said half-beads (60); selectively reflecting light through said non-reflective region (82) of said hemibead further comprising: providing a reflective structure (162) between each adjacent one or more hemibeads (60); and Applying a voltage across the medium (20) causes selective electrophoretic movement of the absorbing particles (26) between a first position and a second position, wherein at the first position the absorbing particles ( 26) Covering the inner surface of said hemi-bead (60) and said reflective structure (162), in said second position said absorbing particles (26) do not cover said hemi-bead (60) or said reflective structure (162) Structure (162). 43. The method according to claim 42, further comprising forming said reflective structure (162) to protrude inwardly from said inner surface of said transparent plate (12). 44. The method of claim 43, further comprising forming the reflective structure (162) to have a hemispherical shape. 45. The method of claim 43, further comprising forming the reflective structure (162) to have a high curvature such that a majority of light incident on the reflective structure (162) undergoes total internal reflection. 46. The method of claim 43, further comprising forming said hemibead (60) and said reflective structure (162) by: softening said transparent plate (12); and Closely spaced spherical bead sections are embedded into said transparent plate (12). 47. The method of claim 43, further comprising forming said hemi-bead (60) and said reflective structure (162) by: Provide circular perforated netting; softening said transparent plate (12); applying pressure to said transparent plate (12); and The mesh is pressed into the transparent plate (12).

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