Sealed letters, postcards and like confidential sheets, and paper, continuous form or document sheet for preparing same

A confidential sheet in the form of a sealed letter, postcard or the like and having a sheet body bearing the information to be concealed on one surface thereof, the confidential sheet being formed in a lapped state by folding the sheet body in at least two with the information bearing surface inside. The body comprises means for preventing the information from being seen through from outside. A paper for preparing the confidential sheet has a body bearing information on one side thereof and comprising means for preventing the information from being seen through the other side thereof. A continuous form for successively making a plurality of sealed letters, postcards or like confidential sheets bearing concealable information, the body of the form bearing the information on one side thereof and comprising means for preventing the information from being seen through the other side thereof. A document sheet for preparing a sealed letter, postcard or like confidential sheet bearing concealable information, the body of the document sheet bearing the information on one side thereof and comprising means for preventing the information from being seen through the other side thereof.

FIELD OF THE INVENTION 
The present invention relates to postal sheets, such as sealed letters and 
postcards, for use in holding communications or the like confidential, 
confidential sheets, such as credit cards, certificates, receipts and 
business forms, bearing information to be held in secret, and paper, 
continuous form or document sheet for preparing such confidential sheets. 
BACKGROUND OF THE INVENTION 
Prior Art 
Heretofore known are confidential sheets adapted to bear concealed 
information to assure secrecy and continuous strips for forming such 
sheets. For example, envelope sheets or strips and envelopes or the like 
prepared therefrom are disclosed in Examined Japanese Patent Publication 
SHO 51-30830, Examined Japanese Utility Model Publication SHO 59-41113, 
Unexamined Japanese Utility Model Publication SHO 60-142970, etc. 
With reference to FIG. 24, such an envelope 10d comprises a first piece of 
paper 1d having an address bearing area 2d on its front surface, a second 
piece of paper 1e having an information bearing area 3d on its front 
surface and a third piece of paper 1f which are integral with one another 
with folds 4d, 4e formed therebetween. Adhesive coatings 5d, 6d are formed 
at the outer peripheral portion of the combination of the second and third 
paper pieces 1e, 1f on the front surface and at the outer peripheral 
portions of the first and second paper pieces 1d, 1e on the rear surface. 
The three pieces 1d, 1e, 1f as folded in three are joined together with 
the adhesive coatings 5d, 6d. 
Problem of the Prior Art 
The sealed letter 10d generally has a concealing effect because it is 
folded in three, whereas since the body of the letter comprises a sheet of 
thin paper, the interior of the letter can be seen through against the 
light of a fluorescent lamp, the sun or the like, and it is therefore 
likely that the information written in the information bearing area will 
be legible undesirably. Thus, the letter has the fatal problem that 
although inherently intended to hold the information confidential, the 
letter fails to ensure full secrecy. 
SUMMARY OF THE INVENTION 
The main object of the present invention, which has been accomplished to 
solve the above problem, is to almost completely prevent the information 
in the information bearing area from being seen through and to ensure a 
more reliable effect to maintain secrecy. 
To fulfill the above object, the invention provides sealed letters, 
postcards and like confidential sheets, and paper, continuous form or 
document sheet for preparing such confidential sheets. The confidential 
sheet is in the form of a sealed letter, postcard or the like, has a sheet 
body bearing the information to be concealed on one surface thereof, and 
is formed in a lapped state by folding the sheet body in at least two with 
the information bearing surface inside. The sheet is characterized in that 
the body comprises means for preventing the information inside thereof 
from being seen through from outside. 
The paper for preparing the confidential sheet is characterized in that the 
body of the paper comprises means for preventing information written on 
one side thereof from being seen through the other side thereof. 
The continuous form is adapted to successively make a plurality of sealed 
letters, postcards or like confidential sheets bearing concealable 
information and is characterized in that the body of the form comprises 
means for preventing information written on one side thereof from being 
seen through the other side thereof. 
The document sheet for preparing the confidential sheet is characterized in 
that the body of the document sheet comprises means for preventing 
information written on one side thereof from being seen through the other 
side thereof. 
Thus, the preventing means prevents the inside of the confidential sheet 
prepared from the above paper, continuous form or document sheet from 
being seen through even against rays, with the result that the information 
written inside is illegible from outside. 
Since the information is prevented from being seen from outside by the 
above means even when rays of a fluorescent lamp, the sun, etc. are used, 
the sealed letters, postcards and like confidential sheets of the 
invention have the outstanding advantage that the information written on 
the sheet can be held in secret more reliably and completely than 
heretofore possible. 
The paper of the invention, incorporating the above preventing means for 
making confidential sheets, has the great advantage that when made into 
strips or dimensioned to a specified size, the paper affords sealed 
letters, postcards and any other confidential sheets with an excellent 
effect to maintain secrecy for business or personal use.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Embodiments of the invention will be described below. 
FIG. 1 (a) is a front view of a postcard embodying the invention, FIG. 1 
(b) is a rear view of the same, FIG. 1 (c) is a view in section taken 
along the line A--A in FIG. 1 (a), FIG. 1 (d) is a view in section taken 
along the line B--B in FIG. 1 (a), FIG. 1 (e) is an enlarged sectional 
view of the portion (C) in FIG. 1 (d), FIG. 1 (f) is a view in development 
showing the front view of the postcard, and FIG. 1 (g) is a view in 
development showing the rear side of the same. 
With reference to these drawings, the body of a postcard, 1, comprises 
three pieces of paper of the same size, i.e. a first piece 1a, second 
piece 1b and third piece 1c which are integral with one another with folds 
4a, 4b formed therebetween. The first piece 1a has on its front side an 
address bearing area 2 where the name of an addressee and his address are 
printed. Each of the second and third pieces 1b, 1c is provided on its 
front side with an information bearing area 3 having printed therein a 
communication or like information. The second and third pieces 1b, 1c are 
folded along the fold 4b with the respective information bearing areas 3, 
3 inside and joined together with a hotmelt adhesive coating 5 formed on 
the outer peripheral portion of combination of these pieces. An adhesive 
coating 6 is formed also on the outer peripheral portion of the 
combination of the first and second pieces 1a, 1b on the rear side 
thereof. These pieces 1a, 1b are folded along the fold 4a and have their 
opposed rear surfaces joined together with the adhesive coating 6. 
Indicated at 7 is a publicity-advertisement area provided on the rear 
(outer) side of the third piece 1c. 
As shown in FIG. 1 (e), the postcard body 1 comprises two front and rear 
sheets of paper 8, 8 and a nontransparent sheet 9 interposed therebetween 
and in the form of an aluminum film formed by vacuum evaporation, the body 
1 thus having three layers. 
The body 1 of the present embodiment, i.e. postcard 10, has the 
above-mentioned three layers, that is, the two sheets of paper 8, 8 and 
the nontransparent sheet 9, so that the inner side of the body 1 is 
separated by the nontransparent sheet 9, whereby the information written 
in the information bearing areas 3 on the inner side of the body 1 is made 
illegible from outside. Accordingly, the postcard reliably holds the 
information secret from a third party while it is mailed from the 
addresser to the addressee. 
The three-layer structure including the intermediate nontransparent sheet 9 
in the form of a vacuum-deposited aluminum film gives enhanced strength to 
the postcard body 1 in its entirety, rendering the body less susceptible 
to breaking. 
Moreover, water, even if deposited on the postcard 10, is blocked by the 
nontransparent sheet 9, which therefore obviates the likelihood that the 
characters and the like on the inner side of the body 1 will be obscured 
or disappear. 
The recipient of the postcard opens the card by cutting off the outer 
periphery thereof as with a pair of scissors, whereupon the information on 
the exposed areas 3 can be readily read. 
Next, a continuous form will be described which embodies the invention for 
making the postcard described. 
FIG. 2 (a) is a fragmentary front view of the continuous form, and FIG. 2 
(b) is a fragmentary rear view of the same. 
With reference to these drawings, the body 11a of a continuous form 11 
comprises a multiplicity of unit slips 14 integrally arranged vertically 
and each including a first piece of paper 1a, second piece of paper 1b and 
third piece of paper 1c. These pieces have the standard size of the 
postcard and are formed integrally as arranged horizontally with folds 4a, 
4b provided there-between. 
The first piece 1a has an address bearing area 2 on its front side. Each of 
the second and third pieces 1b, 1c is provided on its front side with an 
area 3 for bearing a communication or like information. An adhesive 
coating 5 is formed on the front side of the combination of second and 
third pieces 1b, 1c at its outer peripheral portion, while an adhesive 
coating 6 is formed on the rear side of the combination of first and 
second pieces 1a, 1b at its outer peripheral portion. 
The body 11a has a three-layer structure comprising a pair of front and 
rear sheets of paper 8, 8 and a nontransparent sheet 9 in the form of a 
vacuum-deposited aluminum film. 
An ear piece 15 extending longitudinally of the body 11a is formed at each 
side edge thereof with cutting perforations 13 formed therebetween and has 
a multiplicity of punch holes 12. 
Postcards such as the one described above are prepared from the continuous 
form 11 of the above construction in the following manner. 
As seen in FIG. 3, the elongated continuous form 11 as rolled up is 
installed in place and is paid off for transport. 
Next, the names of addressees and their addresses are printed on the first 
pieces 1a each in the specified address bearing area 2 as seen in FIG. 4, 
and a communication is printed on the information bearing areas 3 of the 
second and third pieces 1b, 1c using the printer of an electronic computer 
and utilizing the punch holes 12 at opposite side edges of the form 11. 
After the specified items have been printed as above, the ear pieces 15 
having the punch holes 12 are removed from the side edges of the form 11 
along the perforations 13 as seen in FIG. 5. 
Subsequently, the continuous form 11 is folded in three along the fold 4a 
between the first and second pieces 1a, 1b and along the fold 4b between 
the second and third pieces 1b, 1c as shown in FIG. 6, and the first 
pieces 1a are affixed to the second pieces 1b, and the second pieces 1b to 
the third pieces 1c with the hotmelt adhesive coatings 5, 6 by application 
of heat and pressure. 
In this step, the folded pieces are heated under pressure by being passed 
between rollers and can therefore be joined to one another without 
trapping any air therebetween. 
As seen in FIG. 7, the continuous form 11 is thereafter severed in 
succession along transverse cut lines 16, whereby postcards 10 like the 
embodiment 1 can be prepared automatically by a continuous operation. 
Next, paper for making postcards like those described above will be 
described as another embodiment of the invention. 
FIG. 8 (a) is a fragmentary front view of the postcard making paper, and 
FIG. 8 (b) is an enlarged view taken along the line D--D in FIG. 8 (a). 
With reference to these drawings, elongated paper 17 for making postcards 
has a body 17a with a three-layer structure which comprises a pair of 
front and rear sheets of paper 18, 18 and a nontransparent sheet 19 in the 
form of an aluminum film formed by vacuum evaporation. 
Postcards are prepared from the paper 17 having the above structure by 
forming punch holes 12, like those already described, in opposite side 
edge portions of the paper 17 and the desired address bearing areas 2, 
etc., then forming adhesive coatings 5, 6 to obtain the same postcard 
forming continuous form 11 as seen in FIG. 2, and subjecting the form 11 
to the steps of FIGS. 3 to 7. 
With the embodiment of postcard of FIG. 1, the adhesive coating 6 on the 
rear side of the combination of first and second pieces 1a, 1b is formed 
only at the peripheral portion, whereas the adhesive coating 6 may be 
formed over the entire rear side as seen in FIG. 9. 
In this case, the second piece 1b can be separated from the third piece 1c 
after the postcard is opened, but the first piece 1a remains affixed to 
the second piece 1b with the adhesive coating on the entire rear side of 
these pieces, with the result that at least the first and second pieces 
1a, 1b can be handled like a single piece of paper. The postcard can 
therefore be opened only between the second and third pieces 1b, 1c. 
Accordingly, the postcard will be opened as if it were folded in two to 
expose only the inherently necessary information bearing areas with the 
unnecessary areas left unexposed. This enables the recipient to recognize 
the information bearing areas with extreme ease immediately after opening 
the card and is therefore advantageous. 
Since the first and second pieces 1a, 1b are joined together with the 
adhesive applied to the entire opposed surfaces thereof, there is no 
likelihood that the postcard will have an inadvertently increased 
thickness due to trapped air. This results in the advantage that the 
postcard provided meets the stringent standards as to the thickness, 
weight, etc. 
FIG. 10 (a) is a front view showing another embodiment of postcard, FIG. 10 
(b) is a rear view of the same, FIG. 10 (c) is a view in section taken 
along the line E--E in FIG. 10 (a), and FIG. 10 (d) is a view in section 
taken along the line F--F in FIG. 10 (a). 
With reference to these drawings, the body 1 of a paper postcard 1 
comprises two sheets 20a, 20b folded over each other along a fold 21 and 
joined together with a hotmelt adhesive coating 5 formed over each of the 
opposed surfaces thereof along its three edges. 
One of the sheets, 20a, has an address bearing area 2 on its outer side as 
shown in FIG. 10 (a). The outer side of the other sheet 20b bears the name 
of a company 22 as the sender, and a public notice or advertisement 
printed in color. 
Each of the sheets 20a, 20b has an information bearing area 3. 
Indicated at 42 are perforations serving as means for opening the body 1, 
i.e., for separating the two sheets 20a, 20b joined together with the 
adhesive coatings 5. 
Since the postcard 10 of the present embodiment comprises two sheets 20a, 
20b joined together with the adhesive 5 applied to the three edge portions 
of each sheet, the message printed on the inner side of the sheets 20a, 
20b is completely concealed by these pieces 20a, 20b and therefore 
completely held confidential during mailing. 
With the present embodiment as is the case with the foregoing embodiments, 
the postcard body 1 comprises three layers, i.e., two pieces of paper 8, 8 
and a non-transparent sheet 9. Accordingly, the inside information will in 
no way be seen through from outside but can be held in secret effectively. 
On the other hand, the recipient of the postcard 10 can easily open the 
body 1 as seen in FIG. 12 to readily recognize the information by cutting 
off an ear piece 40 along the perforations 42 as shown in FIG. 11. 
Thus, the postcard of the present embodiment is adapted to hold the message 
or the like in secret, is easy to open and has a novel but simple 
structure comprising two sheets of paper 20a, 20b only. 
The postcard 10 is prepared from a document sheet 10a shown in FIG. 13. 
More specifically, postcards such as the one shown in FIG. 10 are prepared 
by feeding a multiplicity of such sheets 10a one after another to a laser 
printer or the like to print the contemplated items in the address area 2 
and information bearing areas 3 of each sheet 10a, folding the sheets in 
two by a folding machine, and joining the opposed portions of each sheet 
10a with an adhesive by application of pressure with rollers or the like. 
In this case, both sides of the sheet 10a can be printed on by the laser 
printer. 
FIG. 14 (a) is a front view showing a document sheet, as another 
embodiment, for making a sealed letter, FIG. 14 (b) is a rear view of the 
same, FIG. 15 (a) is a front view of the letter made from the sheet of 
FIG. 14, FIG. 15 (b) is a rear view of the same, and FIG. 15 (c) is a view 
in section taken along the line G--G in FIG. 15 (a). 
This embodiment has the same structure as the embodiment of FIG. 1 in that 
an address bearing area 2 is formed on the front side of a first paper 
piece 1a but differs therefrom in that it has an information bearing area 
3 on the rear side of each of the first paper piece 1a, second paper piece 
1b and third paper piece 1c. 
The second piece 1b has a publicity-advertisement area 7 on its front side. 
An adhesive coating 5 is formed on the rear side of the first and second 
pieces 1a, 1b at their upper and lower edge portions. Spots of adhesive, 
5a, are also formed along the outer side edge of the first piece 1a on the 
rear side. 
With the present embodiment, the first and third pieces 1a, 1c are folded 
over the second piece 1b, so that the inner side of all the three pieces 
1a to 1c is concealed. Accordingly, the three surfaces of the paper pieces 
are usable as the information bearing areas 3 as seen in FIG. 14 (b). The 
embodiment therefore has the advantage of being capable of bearing an 
increased amount of information. 
The letter can be readily opened by cutting off the upper and lower edge 
portions of the body 1 inwardly of the adhesive coatings 5 and separating 
off the outer side edge of the body 1 where the spots of adhesive 5a are 
formed. 
The sealed letter 10 of this embodiment is prepared by printing the 
contemplated items on the address bearing area 2 and the information 
bearing areas 3 of the document sheet 10a shown in FIG. 14, inwardly 
folding the sheet 10a in three and joining the folded pieces together 
under pressure with the adhesive coatings 5 and spots 5a. 
FIG. 16 (a) is a front view showing another embodiment of document sheet 
for making a sealed letter, and FIG. 16 (b) is a rear view of the same. 
This embodiment is in common with the embodiment of FIG. 1 in that an 
address area 2 is provided on the front side of a first paper piece 1a, 
with information bearing areas 3, 3 on the front side of second and third 
paper pieces 1b, 1c, but differs therefrom in that the information bearing 
area 3 is provided also on each of the first and second pieces 1a, 1b on 
the rear side thereof. 
Further with the present embodiment, spots of adhesive, 5a, are applied to 
the rear side of the third piece 1c and the rear side of the first piece 
1a, each at its outer side edge, such that like the embodiment of FIG. 14, 
the letter can be entirely laid open. 
This embodiment has the advantage of being capable of bearing an increased 
amount of information because the information bearing area 3 can be formed 
on four surfaces of paper pieces. 
Like the postcard of FIG. 1, the document sheet is folded in three 
generally in a Z-form to provide the sealed letter. 
FIG. 17 (a) is a front view showing a postcard as another embodiment, FIG. 
17 (b) is a view in section taken along the line H--H in FIG. 17 (a), and 
FIG. 17 (c) is a view in section taken along the line I--I in FIG. 17 (a). 
With reference to these drawings, the body 1 of the postcard 41 shown is in 
the form of a single sheet of paper including three pieces 1a, 1b, 1c 
which are integral with one another and identical in size. The piece 1a 
has an address bearing area 2 on its one side. The pieces 1b, 1c each have 
an information bearing area 3 on one side. The two pieces 1b, 1c are 
folded along a fold 4 with the information bearing areas 3, 3 inside so 
that only the first piece 1a with the address area 2 is projected beyond 
the other pieces 1b, 1c. The peripheral portions of the lapped pieces are 
joined together with a hotmelt adhesive 5. The postcard body 1 thus folded 
has an overall size meeting the standard for the postcard. 
With the postcard 41 of the present embodiment as folded in two as stated 
above, only the first piece 1a having the address area 2 is exposed and 
projected outward from the second and third pieces 1b, 1c having the 
information bearing areas 3, so that the name of an addressee, his 
address, communication and like items can be printed on one side of the 
postcard body without impairing the function to hold the information in 
secret and free of any interference with the address area. This permits 
the use of an automatic printer or the like for automatically printing the 
desired items, consequently making it possible to automatically produce 
confidential postcards of the doubled type in large quantities. 
Further because the postcard body 1 as folded in two is dimensioned in its 
entirety to the standard size, the postcard has the advantage that it can 
be mailed as such in conformity with the postal regulation. 
The recipient of the postcard 41 can easily open the body 1 to readily 
recognize the information as seen in FIG. 19 by cutting off the pieces 1b, 
1c at their inner side edge portions from the piece 1a with a pair of 
scissors as seen in FIG. 18. 
FIG. 20 (a) is a front view showing another embodiment of document sheet 
for making a sealed letter, and FIG. 20 (b) is a rear view of the same. 
The body 28 of this document sheet comprises six paper pieces 28a,28b, 
28c,28d, 28e, 28f which are integrally formed. The first piece 28a has an 
address area 29 on its front side. The second piece 28b has a 
publicity-advertisement area 31 on its front side. Information bearing 
areas 30 are formed on the front side of the fourth, fifth and sixth 
pieces 28d, 28e, 28f and on the rear side of all the pieces 28a to 28f. 
Adhesive coatings 5, 6 are formed at one side edge of the body 28 on the 
front and rear sides thereof, respectively. Spots of adhesive 5a are 
applied to the front side of the fourth, fifth and sixth pieces 28d, 28e, 
28f along their inner side edges and along the upper edge of the fourth 
piece 28d generally in an inverted L-shaped arrangement. 
The sheet is folded in six as seen in FIG. 21 as by an automatic folding 
machine, whereby a sealed letter 32 can be obtained as illustrated in 
FIGS. 22 (a) and (b). 
This embodiment has nine information bearing areas 30 in total on both the 
front and rear sides of the body 28 and therefore has the advantage of 
being capable of bearing an exceedingly larger amount of information than 
conventional sealed letters. 
With the embodiments described above, the body 1 of the postcard has the 
three layers of front and rear sheets of paper 8, 8 and the nontransparent 
sheet 9 therebetween as means for preventing the information in the area 3 
from being seen through from outside, whereas the preventing means is not 
limited to this structure. 
For example, the nontransparent sheet 9, which is a vacuum-deposited 
aluminum film, may alternatively be a colored film, nontransparent paper 
or aluminum foil. A colored adhesive may be provided between the two 
sheets of paper to serve as a substitute for the nontransparent sheet 9. 
Instead of using the nontransparent sheet 9, a sheet of paper may be 
directly coated with aluminum by vacuum evaporation to provide the 
preventing means. 
In any case, the preventing means is not limited specifically. 
The sheet material for providing the postcard or sealed letter is not 
limited to paper used in the foregoing embodiments. For example, synthetic 
resin sheets are usable. It is also possible to use a biaxially oriented 
polypropylene film prepared by expanding a biaxially oriented 
polypropylene. 
Accordingly, the term the "paper" for use in the present invention for 
preparing the confidential sheet not only refers to paper in a narrow 
sense but is also used in a broad sense including synthetic resin paper 
and the like. Thus, the term means a plain sheet before printing. 
The synthetic resin material to be used must be coated with an ink so as to 
be amenable to writing. 
As an example of application of a synthetic resin material, FIG. 23 shows a 
sheet which comprises paper 23, and a synthetic resin sheet 24 affixed to 
the paper with an adhesive 25 and coated on its outer surface with an ink 
26 for rendering the sheet 24 amenable to writing. The rear surface of the 
sheet 24 is coated with aluminum by vacuum evaporation (not shown) to make 
the sheet 24 nontransparent on the rear side. 
In any case, the synthetic resin material, when included in the sheet body, 
produces an effect to maintain secrecy by concealing and further gives 
enhanced strength and prevents penetration of water as already stated. 
Although the foregoing embodiments have been described with reference to 
postcards and sealed letters, the confidential sheet of the invention is 
not limited to use as these articles but is also usable, for example, for 
credit cards, certificates, greeting cards, receipts, business documents 
and the like. Thus, the present sheet can be used as any sheetlike article 
for confidential or concealing purposes regardless of whether it is 
intended for postal use. 
Furthermore, the location where the adhesive is to be applied is not 
limited to those of the above embodiments but can be altered as desired 
depending on the type or structure of the confidential sheet. 
The adhesive is not limited either to the hotmelt type used in the above 
embodiments, while the adhesive per se is not essential to the present 
invention; the means for joining the paper sheets together is not limited 
specifically. 
Furthermore, the confidential sheet can be opened by cutting as with 
scissors, by separation along perforations or by any other means. 
Printing of publicity notices or advertisements is of course not essential. 
The continuous form or document sheet of the above embodiments is used 
primarily for business uses for automatically preparing a large quantity 
of postcards, sealed letters or like confidential sheets, whereas such 
form or sheet is not always limited to business uses but is also 
applicable to personal or family uses. 
For family uses, the document sheets shown for example in FIGS. 13, 14, 16, 
etc. may be sold at stationary stores for consumers. The person purchasing 
such a sheet will fill out the sheet, fold the sheet in two or three and 
press the fold as by ironing, whereby the desired postcard or the like 
will be readily made. 
Accordingly the method of writing information in the area 3 is not limited 
to printing but handwriting may also be resorted to. 
Further the number in which the sheet is to be folded is not limited to two 
or three insofar as the sheet is in a lapped state as folded in at least 
two. The term "lapped state" is to be interpreted as including such a 
state of the confidential sheet as prepared by folding the sheet body 
first and then cutting the fold portion. 
The means to be employed in the process for preparing various confidential 
sheets, the procedure therefor, etc. are not limited specifically. 
The confidential sheet is not limited either, in size or shape but can be 
sized or shaped differently as desired according to the type of the sheet. 
For example, postcards need to be sized in conformity with the postal 
regulation.